# Building a Garden Office Advice Required



## Markymark

Hi All

I am attempting to build a 14' x 10' Garden Office from 2"x4" Frames and a Pitched roof. I have never undertaken such a task and have downloaded a basic frame shed plan to give me an idea how to form a window opening and a door opening in a stud wall. I am going to clad it with ship lap (Tanalised) and then fit kingspan or equivelent batts in the wall and then clad internally with 1/4" Ply. Please can anyone advise me the best way to form a pitched roof and how to cut the correct angles for the roof timbers? Any other hints and tips would be welcomed as I do beleive in learning from others mistakes. 

Another challenge is that my back garden is quite steep and requires at least four posts/ columns to sit the floor frame on to level it up. Can anyone advise what the best method of installing these would be. Cost sensitive of course. 

Awaiting your comments

Mark


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## laird

Starting at the bottom, I think you'll need a lot more than 4 posts to level it. A simple way is to dig drainage pipe (min 8" dia) in - the depth depends upon the soil and slope - and fill with postcrete.


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## cambournepete

I don't want to be a party pooper - but check whether you need planning permission - we're inspecting a plan for a garden office at our next council planning meeting.


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## Markymark

Thanks

I did check with planning and they say I can put a shed in the rear garden with a height of less than 3 metres as long as it is more than 2 metres from the boundary.


I do like the idea with the concrete piles. Not sure I can get deep enough as the ground has a lot of flint in it. What do you think to stacking concrete blocks set in motor at each corner and maybe in the centre also?

Mark


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## jasonB

If its going to be 10ft wide then you won't get much of a fall on the roof if you are to keep it below 3.0m, maybe a monopitch would be better and it will also depend wher they measure the height from if its on sloping ground.

You would still need to dig out some soil to get a firm footing for the block piers to sit on so either way its going to involve some digging. And remember the longer the span between piers the thicker your floor joists will need to be thus reducing overall height.

Jason


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## jasonB

Just remembered this series of photos of a nice office build may be of some use, can't remember who it was now may have been a member here once or on another forum

http://s220.photobucket.com/albums/dd6/ ... ?start=all

Jason


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## laird

Markymark":1346apn3 said:


> Thanks
> .....................I do like the idea with the concrete piles. Not sure I can get deep enough as the ground has a lot of flint in it. What do you think to stacking concrete blocks set in motor at each corner and maybe in the centre also?
> 
> Mark


Do you have an HSS or similar near you ? Hire a petrol auger, strain taking fence post digger. 1 day should do it. I'd dtill be looking at posts a lot closer together than 7 feet, maybe 18"/2feet tops.


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## chipchaser

Hi Mark,

what is the slope on your site and which way will the building sit relative to the slope? 

When you say needs 4 posts were you thinking one at each corner?

I guess you don't want a solid concrete slab base but are looking at timber joists with a ply floor. 

What sort of stuff might go into the proposed garden office? I am thinking in terms of weight and the floor loading.

Graham


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## Deejay

Mornin' Mark

Have you seen this sticky ...

https://www.ukworkshop.co.uk/forums/buil ... 39389.html

I don't think Mike is very active here, but you could try The Wood Haven site.

When you've decided on the size and type of roof etc.

http://www.blocklayer.com/

might be useful.

Don't forget to post pictures.

Cheers

Dave


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## chipchaser

HI Mark,

this site has tables for floor and ceiling joists and rafters

http://www.home-extension.co.uk/tech2.html

this site has a calculator for floor joists and one for roofing but, as far as I can see, covering quantities rather than structural sizes

http://www.tommy-software.co.uk/

Hope that is of some use

Graham


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## Markymark

Thanks everyone 

This is a great help. I feel I still need some help with the foundations and floor joist layout. The Office is going to house the usual Desk and 4 draw filing cabinet. PC and Printer and may be a two seater settee.

Any more help gratefully recieved.


PS Like the calculators [/code]


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## Markymark

chipchaser":2p1xl9tw said:


> Hi Mark,
> 
> what is the slope on your site and which way will the building sit relative to the slope?
> 
> When you say needs 4 posts were you thinking one at each corner?
> 
> I guess you don't want a solid concrete slab base but are looking at timber joists with a ply floor.
> 
> What sort of stuff might go into the proposed garden office? I am thinking in terms of weight and the floor loading.
> 
> Graham



Hi Graham 

I am trying to work out how to attach photos. The back garden is on an incline up to a small coppice which is where I want to site the time framed office on a floor made of joists and a frame. This is to be suspended and levelled by what ever means possible. My initial thought was three concrete piers at the front and the rear of the shed would almost be sitting on the ground. I am a novice at this so need some coaching. I was going to hire a builder to make the block or concrete piers to sit the frame on. I think I can go to 3m high as I am more than 2 metres away from the boundary.

Thanks Mark


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## Deejay

Morning Mark

I am trying to work out how to attach photos.

See ...

https://www.ukworkshop.co.uk/forums/addi ... 14776.html

Cheers

Dave


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## Markymark

Ok Here goes

I have posted three photos of the potential site of the garden office. 

Not sure if you can get the feel for the incline. The office is going in a clearing in the copse. There will be roots and plenty of Stones and Flint to deal with.

What I would like to know is using 2x6 or 2x8 construction grade timber how many concrete filled posts would I need to create to sit the suspended timber floor on.


http://www.flickr.com/photos/[email protected]/?saved=1


Thanks 

Mark[/url]


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## ByronBlack

Markymark":wek2ltxi said:


> Ok Here goes
> 
> I have posted three photos of the potential site of the garden office.
> 
> Not sure if you can get the feel for the incline. The office is going in a clearing in the copse. There will be roots and plenty of Stones and Flint to deal with.
> 
> What I would like to know is using 2x6 or 2x8 construction grade timber how many concrete filled posts would I need to create to sit the suspended timber floor on.
> 
> 
> 
> 
> 
> 
> 
> Thanks
> 
> Mark








Mark - you need to put the link to the actual image in the brackets rather than the page url..


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## Markymark

Thanks. Tried the img tag but all it did was put img and /img at either end of the text. 

Mark


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## big soft moose

Markymark":2fhaw0eu said:


> Thanks. Tried the img tag but all it did was put img and /img at either end of the text.
> 
> Mark



they need to be in square brackets and also not to have any spaces between the img tag and the file url (also the url must end in the file extension ie .jpeg, .gif, etc )


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## Markymark

Thanks to ByronBlack the images are now published. See previous page for location of shed.

Mark


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## jasonB

I would check again with your local authority as they may well measure the 3.0m height from the lowest ground level, so whats 3.0m at the back of the office could be getting close to 4.0m at the front. It may mean you have to cut into the bank so you can have 3.0m all the way, it wouldn't need a retaining wall as the ground could be angled back.

I would have thought one pier in each corner and one mid span of the long edges would do you, so six in total. Double up 8x2s to form a perimiter beam and then use joist hangers to support 8x2 joists spaning the 3.0m width.

Jason


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## Markymark

Thanks Jason

I feel thats good advice. Do you think 6x 8" circular concrete piers will suffice assuming they go deep enough to reach clay or bed rock? The use of drainage tubes as formers or do you think it will need bigger mass filled holes and a larger pier? 

I am checking with Planning and Building control. I await there decision.

The next help I will need is completing a Mono pitch roof. What Pitch and what coverings?

Thanks for the help so far all.

Mark


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## jasonB

If you have got bed rock then the piers can come off that. You are more likely to have a firm subsoil and will need a larger bearing area.

As a general guide as I don't know your soil something like digging a hole down 600mm that is 450x450. Pour 150mm of concrete into this to form a pad. You and stick a bit of rebar into that before it sets and this will tie the concrete tube infil to the base. Stand your tubes onto these pads and cut so all the tops are level and the shortest 100mm above ground level.

When set place a piece of DPC onto the top of the pier and then you can position your ring beam.

For a mono pitch the easiest way is just to make one long side taller than the other and have the ends with a sloping top. You can then either just fix joists to the top of the 2 long walls and cover with ply and felt. Or you could think of using a profiled metal roof, these can be had with rigid insulation bonded on and may well span the 3.0m without any other support.

Jason


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## Markymark

Great. I would like the roof to be quite a attractive feature and when I was considering a pitched roof I was thinking of using wood shingles. Was the profiled metal roof the corrugated type? If I could get a multi layered roof covering so that if one perishes it has a backup. I will research roof coverings. 

Great advice as usual.

Mark


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## chipchaser

Hi Mark,

Interesting photos but more info needed to advise in detail. I suggest you drive 4 poles, one at each corner into the ground where you intend to site the building. Tall enough to show the intended eaves height would be useful. Attach roofers tiling lath horizontal around the four sides starting at the highest ground level (GL). Measure down to GL at the 3 lower points and record the dimensions. Mark the eaves on your posts with a horizontal offcut of lath. Take a photo and post it, with your dimensions to GL, in this thread.

It would be useful to establish what ground you have so you can decide how you will make the foundations. I would dig a couple of pits one at centre of the high end and likewise at the low. The top 6” or so of soil is generally organic topsoil not representative of the sub soil, I would go down about 24”.

Mono pitch roofs can have more rise than you might want with some roof coverings. The appearance is always a personal matter but you have the planning height restriction to comply with. You mention wood shingles. Info on these here:

http://www.cedarbureau.org/installation ... page23.htm

The only problem with the info is that they (USA & Canada) use “exposure”, rather than cover, and pitch ratio (i.e. 3:12) not degrees but basically 14 degrees is absolute minimum 18 degrees safer in wet UK and personally I think they look better at more traditional pitches of 30 degrees and above. Shakes are riven, shingles sawn and all come in random widths. They can be a challenge to lay to ensure correct side cover.

Every roofing material has its minimum pitch, generally smaller units must lie at a steeper pitch to exclude water. The corrugated bituminous sheets are cheap and easy to lay and seem less prone to leak than felt. If you use them provide frequent purlins, or battens if you use rafters, because they are prone to sag between supports. Better still lay them on a ply deck.

Hope that is helpful

Graham


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## Markymark

OK. Thanks for all the help so far.

The local Council have come back and rejected the Mono pitched roof option if the Eaves height is in excess of 2.5M from the ground. That being said I can have a dual pitched roof with a height of 4M and a eves height of 2.5M. Now I assume the dont mean the ridge height? 

I have to talk to them with regards to which part of the sloping ground they are taking their measurements from. I will assume it is the lowest ground level. 

I feel that a eaves height of 2.5 M on a mono pitched roof will feel claustrophobic as I am 6' 3". With a dual pitched roof the feeling of an open pitched roof would allow extra space.

Mark


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## chipchaser

Hello Mark,

the rules allow you to have a maximum eaves height of 2.5m and highest point, which will be the ridge, of 4m with a dual pitch roof. Any other roof form the max eaves height is still 2.5 but max overall height is 3m. If you are within 2m of the boundary the maximum height is 2.5 metres.

This pages sets it all out, with pictures if you click on the mini guide:

http://www.planningportal.gov.uk/englan ... buildings/

Conservation areas, curtilage of listed buildings, etc have stricter rules but your planners should tell you if any of those apply to you.

2.5m is over 8' and if you have a good overhang at the eaves the internal height should be comfortable. What would your minimum acceptable internal height be? You could have roof trusses like this and board below the rafters.











Eaves height of this turned out at 2.4m and internal height below the truss is 7' 1.1/2". But I am 6" shorter than you.

Have the planners actually been to site? I do think the suggestion of marking out with poles is worthwhile as if they come they can see exactly what you propose and confirm what they would expect, most critically where they intend to measure the eaves and ridge heights and so relative to what ground level. If they don't come you can drop a photo into them. Getting the planners on your side at the start is much less stressful than the fallout that can arise if a misunderstanding comes to light when you have finished your build  

If you are not keen to mark the eaves height then at least setting the position and floor plane with shorter posts and confirming the fall of the site is worthwhile.

Regards

Graham


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## Markymark

Thanks Graham

Your shed looks great. Nothing as fancy for the roof. I wonder if the planners would visit the site as I have not paid anything in to the pot. I submitted a Household Enquiry form with all the details on it and they sent me a letter. I can talk to them on Monday. I will see what they say. 
I feel a dual pitched roof will be easier to finish and will look better. I was considering Wood shingles which are difficult to install but look great especially in a woodland setting. I think I read somewhere that the minimum pitch needs to be 6/12 which on a 14 foot length would mean a ridge of 3' 6". Add that to the 2.7 m eaves height and I should be well within the permitted development rules. I feel i will have to explore the levelling of the ground or at least digging out the upper slope so the front elevation will be 2.7m to eaves also. 

Getting itchy feet at the moment and want to start marking out. With posts as you suggested. My only worry is that if I have to dig out the upper slope I do not damage any of the tree roots.

Mark


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## chipchaser

Hello Mark,

And thanks for the kind comment. Its all clad and being used and one day soon I will finish the inside 

You are right, if they have replied and made their comments you shouldn’t have anything to worry about except to confirm which ground level they would measure the eaves and ridge height from, if they ever bothered to check.

Aesthetics are very personal but I agree with you that a traditional pitched roof looks better than a monopitch in most situations. The summerhouse above has cedar shingles which I got from a place in N London, the cheapest I could find but still about £550 collected.

6:12 is 25.5 degrees which is ok for shingles and most alternative shed roof coverings. UK sheds generally tended to have the ridge running along the longest dimension of the building, in your case 14’, to minimise the rafter span whereas garden chalets seem to go the other way which I think is what you intend from the span and rise you mention above. Either work ok. If you use purlins to support the rafters you shouldn’t need ties between the rafter feet on a small building like yours. If the purlins are set at the slope of the roof you don’t need to cut any birdsmouths in the rafters so the carpentry can be really simple. If it is all to be insulated and clad internally, so concealing the carpentry, then galvanised pressed metal clips are quick and adequate to fix rafters.

The point foundations mentioned in earlier posts would minimise any damage to tree roots and, if taken deep enough, avoid later problems that could arise from the trees. You mention above 2.7m at eaves plus approx 1.075m (3’6”) rise to the ridge giving a ridge height of 3.775m. If the fall of your site is less than 0.225m you shouldn’t need to dig out the upper slope. Does your 2.7m dimension allow for the floor structure being above existing ground level?

Apologies if this is stuff you already know/have worked out.

Graham


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## Markymark

Hi Graham

Sorry for the delay..Making the most of the good weather.

I was going to use a ridge beam supported at both ends and nail the rafters to the ridge beam. I assume I would need to do the bird mouth cuts also. My alternative would be roofing trusses not sure if to make them up myself, with the limited knowledge I have, or buy them in? I would like to make all I can as this is my first serious woodworking project I will learn along the way.

Even the terms Purlins, Rafters etc were a foreign language a few weeks ago so it lets you know how little experience I have had.

I am in the process of marking out and digging the holes for the piers. 

I have had conflicting views on the timber to use. Some people say use Kiln dried timber some say air dried as there is less twisting and warping when it is outside and some just say outside stored tanelised timber. I assume I need different source for the externally faced timber and the internally faced timber?


The fall of the land is approx 15 degrees 1' 6" in 10', if that makes sense?

Cheers

Mark


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## chipchaser

Hi Mark,

Here is what I mean. Apologies for the cobwebs but you can see that the purlin sits on a sloping top rail in the first picture, which is how I suggest you might do it. Offcuts provided the blocks which locate the purlins. Your purlins would be closer together and it would be neater to just cut a length of timber into pieces to suit the purlin spacing and use them as solid blocking (noggins).





The second picture shows that where I added this box onto the end of an existing range I simply bolted a timber plate onto the external wall. 





It is a very simple way to form a roof and this video shows assembly of a purlin roofed garage:
http://www.youtube.com/watch?v=0VOV2YvbIP8


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## Markymark

OK New year and my Garden office is underway. I have dug out the footings and filled them with concrete. Now I need to form some piers. The pads for the piers to sit on are approx 18" square with four reinforcement bars. I need either a square hollow concrete block to build a pier or some kind of Concrete former to either make a square or round 3' pier. 

Does anyone know the best way to proceed and where I can get cardboard tubes from?

Thanks

Mark


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## Mcluma

Markymark":2dvrwx0g said:


> OK New year and my Garden office is underway. I have dug out the footings and filled them with concrete. Now I need to form some piers. The pads for the piers to sit on are approx 18" square with four reinforcement bars. I need either a square hollow concrete block to build a pier or some kind of Concrete former to either make a square or round 3' pier.
> 
> Does anyone know the best way to proceed and where I can get cardboard tubes from?
> 
> Thanks
> 
> Mark




I have to check where i got them from, they work perfect, you just cut them with the jigsaw to size

found it

http://www.essextubes.com/piling-pile-caps.html


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## Markymark

Great thanks.


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## Mcluma

I know its a bit late in the game, but this is the home office / cabin i build, this one has a masonette floor in it




dsc0097lg1 by mcluma, on Flickr



dsc0096ue6 by mcluma, on Flickr



dsc0090va5 by mcluma, on Flickr



dsc0088go6 by mcluma, on Flickr



dsc0087ir7 by mcluma, on Flickr


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## Markymark

Ok first dilemma.

I have spaced the floor joists at 600 centres but as the walls are going to be clad with ply i will have to do the wall frames at 2' centres to accommodate a 8' x 4' sheet. This presents problems in that the kingspan or equivalent insulation comes in 600 wide or 1200 wide sections. 

The question is if I was to build a typical stud wall at 600 centres like the floor then the spaces between the studs would be 553mm that is a 600 centre less 47mm ( the size of the stud).

1106 or 553 would not fit any standard insulation in between.


Am i missing something?


MARK


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## No skills

Sorry being dim here.. what sort of insulation are you looking to install? something like celotex poly sheets are pretty easy to cut to fit between studwork.


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## Markymark

Celotex is easy to cut. I thought you could buy insulation to fit inbetween the standard size centres of a stud wall, whatever that may be.

I'm just lazy.

Mark


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## Dibs-h

Markymark":2i7384kf said:


> Celotex is easy to cut. I thought you could buy insulation to fit inbetween the standard size centres of a stud wall, whatever that may be.
> 
> I'm just lazy.
> 
> Mark



The insulation that is 450 or thereabouts wide is really for rafters. As it's precut, works out slightly more expensive. Jsut get the 8x4 sheets and cut it to fit.

HIH

Dibs


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## Markymark

Thanks for the advice.

I feel this is the only viable option.


Upwards and onwards.

Mark


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## Markymark

Ok, I need to clad the timber frame walls to make them rigid. I was going to clad in 11mm OSB as I have budget constraints.

Question is, is 11mm OSB sufficient? Or do i definitely need 18mm? Should I brace any of the four timber frames diagonally and if so can I just brace in between two studs on each frame?

The shed is currently 5m x 4m and in a windy elevation.

Thanks

Mark


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## No skills

Depends on what you want to hang off the cladding, 12mm is fine but if you have something especially heavy to put up and you cant hit the studs with the fixing screws then an upgrade maybe in order - if you do have to upgrade in thickness for some reason then perhaps you can get away with just doing one wall in the thicker material. Have you put any noggins in between the verticle studs?

** sorry just thought, is this for inside or out?? #-o **


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## Markymark

Sorry should have said. 

This is outside cladding which will be Tyvek Housewrapped and then battens attached at 600 centres and then finally clad with shiplap.

The idea of the external cladding was to make the frame rigid before erection on site. 


Thanks 

Mark


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## chipchaser

Hi Mark,

It is usual to put ply or OSB on the inside. There is no rule about this but neither are very vapour permeable so with OSB on the outside the Tyvek would not “breathe” so well and you may get condensation at the dew point trapped within the wall thickness. If you are using Celotex or similar closed cell insulation water vapour cannot condense within the insulation but can on the studs around the edges, or on any surface cold enough. This doesn’t matter as long as the moisture can evaporate and escape when the temperature picks up. 

If you close nail OSB to all the studs, rails etc in each panel you have made a stressed skin panel and diagonal bracing would not be necessary. A big panel made like this can be very heavy.

You probably work much more accurately than I do but keep in mind that a finished panel with a board face or bracing needs to be sufficiently square and of equal height to be sure it all goes together easily without annoying tapering gaps. It is not difficult to line the frame with ply/OSB after it is erected and you can adjust the studs for vertical as you go. A couple of diagonal battens pinned to the first corner stud will hold it vertical and away you go! Fixing the lining afterwards can also cover any minor inaccuracies.

That stable I posted photos of a while back is of ex 2” x 3” planed softwood framing with shiplap on the outside and lined inside to half height with nominally ½” OSB. It has been up for over 14 years and is standing up to “horse wear” well. If you need to hang something very heavy on a wall you can always add another thickness of OSB or ply in that area

Graham


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## Markymark

Hi Graham

Good to hear from you again.

Your probably aware that the front elevation of this shed is elevated so when you are stood on the timber ring beam you are already four foot in the air. That said I would have to get a scafolding tower to board the front frame once it is erected. I opted for making sure the ring beam was square and level and then with that datum create a square frame braced with 11mm OSB on the outside, Like all the house building programs show, I would housewrap this outside and then batton this and clad with shiplap. The inside would be filled with celotex rigid foam insulation and then sealed with a damp proof membrane inside. The damp proof membrane would then be clad with ply to make a finished surface to hang shelving off etc.

The only moisture that should reach dew point is any moisture still trapped in the wood and as I am using tanelised 47x100 timber that may be significant. I hoped that the Tyvek Housewrap breatheable membrane would take care of that. Alternatively I could wait a while until the shell dries out after construction to ensure I dont seal in any problems?

Forgot to mention the wife will be using this as a home office. I knew someone would steal my creation, bless her!

Thanks for the help.

Mark


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## Mcluma

any pics of the progress, you know we love pics


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## Markymark

Some photos hopefully. 





Front elevation of newly installed ring beam and floor.





Another front shot showing 3 ft block piers.





The floor joists Maximum open span 1.9m 6" x 2" Tanalised joints with Galvanized Joist hangers.





Left ring beam shot, Nice!!





Corner showing mitre and bracket attaching the frame to piers.


I will be using this elevated platform to make the wall frames. Wood should be delivered today!!

Mark


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## chipchaser

Re your concern about bracing with OSB and the thickness required.

This is difficult to answer because there are too many unknowns. Alarm bells ring when you say ”in a windy elevation”. I imagine a steep site rising from a cliff looking out to sea in a south westerly direction, the sort of place you could fly a kite made of boiler plate using an anchor chain for a string. Even if we knew how windy, what elevation, what orientation, how exposed is your site and how thick your ply inner lining and shiplap cladding will be you might not get a useful answer!

Bottom line on this is that no one except a structural engineer who from experience of making calculations of wind load on timber framed buildings, or someone with similar knowledge, is likely to hazard giving you an answer. This is because even casual advice given outside a contractual relationship is subject to the law of Tort, i.e. Duty of Care. 

Assuming you don’t want to pay a structural engineer and don’t have any friends or relations in that line I suggest you should look and ask around in your locality. Ask if any sheds in similarly exposed locations have been wind damaged. Look at sheds which have stood the test of time and how they were built.

There is basic stuff about wind loading on buildings in Approved Document A of the Building Regulations, including a map of wind speeds etc, which you can download free from http://www.planningportal.gov.uk/buildingregulations/ . However, to prove a design you need to be familiar with other stuff like BS 6399, BS 5266 and structural calculations.

In my location (middle of UK, open countryside but not severe exposure) I would not bother with OSB on the outside. Hereabouts, shiplap boarding outside and a decent ply lining inside a frame of 47x100 like yours would be more than adequate. You must of course ensure the various elements are adequately tied together to provide horizontal and vertical restraint, to resist wind lift on the roof and possibly the entire building.

A timber house builder could have several reasons to consider OSB on the outside but do they apply to your situation?
 Their panels are usually made off site by a subcontractor in a workshop or factory environment using dry materials so no problem with drying of the frame timbers, but they have to get them to site and erect them undamaged.
 The panels would need to be weatherproof and robust enough to withstand transport on an open lorry, storage outside on site, handling and erection. 
 Wind loading on the partially complete structure, before lateral restraint is provided by floors and roof, is a serious concern. Durability pending final cladding could also be a concern. 
 OSB would be a cheap and effective way to brace the panels and protect the insulation and meet these criteria.

Diagonal bracing between only two adjacent studs will not be very effective. My gut feeling is that an adequately thick sheet of ply or OSB close nailed to the framing will be much more effective than a diagonal brace. When the outer cladding of shiplap is fixed it will provide additional bracing especially if nailed through the battens into the main studs and plates.

Tanalised timber should not be “wet” when sold but it might have a higher moisture content than ideal. I see that your timber should have arrived today so if it is wetter than you would like could you keep it covered somewhere in a stickered stack to dry out before use? If not or you need to press on I would at least leave the inside of the frame exposed for as long as possible before enclosing it.

With respect to drying out, it appears that 11mm, or less, thick OSB may be sufficiently permeable.: 
_“nominal 11 mm (7/16”) or thinner wall sheathing panels will allow a wall cavity containing green stud lumber and glass fibre insulation to reach an equilibrium moisture content below 19 % in about 60 days.”_
http://osbguide.tecotested.com/pdfs/en/tb111.pdf
Note that the same paper says that OSB of 15.5mm or thicker is effectively a vapour barrier so this thickness would not allow any moisture to escape. This info is from Canada and does not necessarily comply with any UK standards or Building Regulations. Another publication on that site states: _“All panels should be spaced 3 mm (1/8”) on all sides to allow for expansion due to moisture changes,”_

Sorry I can’t give you a definite answer to your question. I hope you might find something in the above to help you. Ultimately you need to do what you feel comfortable with. Adding OSB to the outside cannot do any harm and as long as it is 11 mm thick or less the advice quoted above suggests it will be permeable enough. I like your photos, looks like a very nice spot for a home office.


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## Markymark

Thanks Graham 

As usual you have been a real asset to me and this forum. 

I feel the external OSB could be an unnecessary cost. Would I still need to put a breathable membrane on the frame before cladding it? 

I feel I am guilty of watching too many TV programs and not learning the science. 

Anyhow, I will see how it goes. It may be that I will dry wall the inside in that case external cladding. 

Difficult to se the wood for the trees. 


Mark


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## chipchaser

Hi Mark,

Thanks for your kind comments although not sure I recognise myself there.

If you are going to use plasterboard in place of ply for the internal lining I would keep the OSB on the outside. I would put a breathable membrane on the exterior of the panel whether you sheath with OSB or not.

I would then fix battens to space the shiplap cladding away from the breathable membrane as you described before. 

A breathable membrane may not be essential in many workshop sheds due to low levels of water vapour generated. A home office is more like a room in a house than a shed and perhaps you might have a kettle in there to save going to the house for a cuppa. Adding the membrane makes the space flexible for future uses. It also adds another layer of protection against wind driven rain.

I was serious about checking out the local experience in shed construction if your site is more exposed or subject to higher wind speeds than normal.

When I looked at your photos I wondered how you had fixed the floor frame down to the piers. Are the brackets fixed with screws into wall plugs in the joints between the top course of concrete blocks? 

Graham


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## Markymark

Graham 

You can see in the last photo that I have used a strong galvanized L bracket at each intersection. This is attached to the pier using M6 Rawl bolts. The pier is mass filled with Concrete and rebar. 

My immediate problem is the fact that I asked for dry timber, ok that is not a very accurate word, I feel the wood yard have taken me for a ride!! The wood I had delivered is Tanalised but I feel it has been stored in a lake!! 

I have not got the time to sticker stack it so upwards and onwards. I feel I will clad externally with the 11mm OSB (additional cost) that will allow me to do all the work on the outside and get the project finished while allowing the unclad inside to dry out (hopefully). I really don't want to start work on the internal stud work until the moisture level is down or I will risk trapping moisture between the breathable membrane and the damp proof membrane on the internal wall. 

Anyhow progress report - Two side walls built, I should have the other two built in a day or so. Then to build the purlined roof you kindly advised me on. 

P.S. The sheds exposed elevation is looking north westerly and we are about 3 miles off the south coast. I feel as long as I can clad beneath the shed to stop wind trying to lift the shed it should not be a problem. 



I'll post more photos soon. 

Mark


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## Markymark

Progress report or not....


OK I have three of the four sides built and clad with OSB 3. I have checked for square and level along the build. I have asked some friend to come round to help me erect them as the front panel which is 2.4m high and 5.1m long is a little heavy to say the least and as it is to be erected on to the edge closed the incline it may turn in to a sledge.

I thought while I am waiting I would give some thought to the Purlin roof Graham kindly advised me on. The problems arise when I want to create this roof with a overhang at all sides. The Gable is no problem as I can extend the purlins beyond the wall. The eaves however are a different matter I am having problems in visualising a simple way to create a soffit type scenario and imagining how the timbers connect. I will be cladding the roof with 18mm OSB 3 and then cladding with felt tiles. 

Any help appreciated!

Mark


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## kingcod

I am not sure if my design (and its not yet been built!) relates to what you are trying to visualise?

Its an exposed eave soffit with a ventilation hole (mesh behind) and a trim running the length of the roof.

I am using Rob Thallons book 'Graphic Guide to Frame Construction' for tricky bits like this.


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## Markymark

Thanks Kingcod

That looks similar to what I imagine. The difference is that I am creating a Purlin only roof. I think due to my lack of experience with cutting 20 birds mouths... I am beginning to be drawn to the things. I firstly need to create three A frames to support the four 150 x 50 Purlins spanning over the 4m or so.


Thanks for the photo much appreciated.

Mark


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## chipchaser

Hi Mark, sorry don’t look at UKW so often now so missed your post till I saw Charley’s email.

Have a look at page 6 of these lecture notes from City College Coventry

http://learning.covcollege.ac.uk/conten ... s/M123.pdf

and page 43 of this:

http://www.awc.org/pdf/wcd1-300.pdf

Both show a verge detail using a ladder frame to carry a rafter clear of the gable wall. You could use the same design for an eaves detail. I would make sure the overhanging outboard length of the “rungs” of the ladder is equal to or slightly less than the inboard length to minimise the possibility of the verge or eaves sagging under its own weight. Hope that helps.

Sorry to hear about your freshly treated timber. Carcasing timber seems to come like that from some suppliers; Arch have a COSHH leaflet at: 
http://www.archchemicals.com/Fed/WOOD/D ... Timber.pdf

which says:


Treated timber should be surface dry before release
from the treatment plant to the consumer. This is a
requirement under the Control of Pesticides
Regulations for all wood preservatives and has to
be adhered to by timber treatment companies.


If you think it is not compliant you can call HSE and/or Trading Standards and ask them to take a look.

Isn’t your extra cost in OSB wall sheathing mitigated by the saving made by using plasterboard in lieu of ply for the internal lining?

Graham


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## Markymark

Graham

As usual you have excelled yourself. Thanks.

One question, The timber I have purchased is tanalised. I know most wood yards store tanalised timber outside. Does this H&S Legislation apply to tanalith?


Mark


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## chipchaser

Hi Mark, 

That COSHH sheet is issued by Arch who supply the Tanalith chemicals to the treatment plants. 

There are 2 statements in text boxes on that COSHH sheet, both say the timber should be surface dry before use. I understand that is because once dry the chemicals are bound into the timber. I don’t know whether re-wetting the timber, by storage outside etc, releases the chemicals. 

There is another leaflet on their site for consumers:
http://www.archchemicals.com/Fed/WOOD/D ... _Tan_E.pdf 
Handling precautions are stated at top of second page. If, after reading both sheets you still have concerns your best bet would be to ring Arch and ask them for advice.

The product you have should be treated with TANALITH E. The following is from the Arch website:

_TANALISED E pressure treated timber has been impregnated with TANALITH E, a waterborne product based on copper triazole technology. Copper is derived from recycled sources and triazoles are organic biodegradable biocides, commonly used to protect many of the food crops we eat. TANALISED E pressure treated timber is usually specified for both in and out of ground contact applications where there is a medium to high risk of decay or insect attack._

Until a few years ago tanalised timber was treated with chromated/copper/arsenate, now called TANALITH C. Another quote from Arch:

_TANALITH C pressure treated timber has been impregnated with TANALITH C preservative, and is approved for use in markets where CCA (chromated/copper/arsenate) is still permitted for use.

Restrictions apply; for example, the use of CCA is no longer permitted in Europe under the Biocidal Products Directive (BPD). _

Basically E is safer than C and it seems ok for non europeans to be exposed to a higher risk than allowed here, apparently it is popular in Africa. Don’t know whether CCA is still legal in USA and Canada. Somebody else here is bound to know.....

Graham


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## Markymark

Thanks Graham. A fountain of knowledge. 

More photos...











Mark


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## Markymark

Hi All

I need to make the front and back panel walls more rigid against the wind and I am unsure on what to add. The front and back walls are 5.1m long and 2.4m High. The roof rafters will run between the smaller side walls. 

Can anyone help recommend a way of increasing the panel strength against wind loads. I have added wind bracing in all the panels by adding diagonals within the panels. Sadly this does not help in the midpoint of a flat wall.

Thanks

Mark


----------



## chipchaser

Hi Mark,

*1 what is the current state of your progress?* I assume, from what I have seen in your photos and read in your post, that you have 4 walls up but no roof on yet. If thats about right, don't be too worried yet.
*2 How much do the panels deflect when wind loaded?*
*3 Have you fixed the outer cladding or any inner lining yet?*
*4 At what centres are the screws or nails fixing the OSB to the framing?
5 Have you got any temporary bracing in the roof plane?*

Diagonal braces wil only provide resistance to racking they make the panel very little more resistant to bending.
Adding the inner skin and outer cladding layer will stiffen the panels and give more resistance to bending.
Walls without bracing at roof level will be prone to damage if subjected to wind. Temporary bracing will help. If it is constantly windy you will need to put in additional temporary bracing to hold the panels flat whilst finishing the inner and outer cladding. If you fix the sheathing boards onto a bent/twisted/deflected frame you will fix it in that shape permanently  

If you could answer the 5 questions above I will comment in more detail
Graham


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## Markymark

Graham

Here are some current photos of the build. 





















1. I am not sure how to work out the lateral wind deflection on the panels. The two that concern me most are the largest 5.1m panels which are facing east/west. To the west you can see straight over the valley for miles and so is very open and exposed. The front panel which has that great vista also has the wind load and has a large opening in the middle for the upvc french door at 1.2m wide. 

2. The outer cladding is fixed across all the studs but not the noggins. It is fixed with 75mm galvanised nails. I also have some bracing timbers vertically holding the front panel in place and horizontally bracing the corners. These are just temporary and will be removed when I fit the roof. 

3. The centres are 2'.

4. The outer sheathing is 8' x 4' 11mm OSB 3 (stuctural). I am yet undecided on the inner skin.

Do you think I should add more noggins. I have doubled up the studs at the door and windows but not the noggins. 

Hope this gives a clearer picture. 

Mark


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## chipchaser

Hi Mark, thanks for photos and replies:
1. Progress is as I expected, well done to get this far so quickly. 

2. Deflection of the panels under wind load: In your post of the 18th you stated that: 
I need to make the front and back panel walls more rigid against the wind”
Your latest post says:
“I am not sure how to work out the lateral wind deflection on the panels”.
So if you can’t put a figure on how much they deflect - by what measure have you decided you need to make them stiffer? You don’t need to do any working out, calculations are for the design stage and predict how the building is likely to perform under set conditions of loading. I understand your concern with respect to the front and back panels in particular but I would want to quantify how much they move and use that information to confirm whether concern is justified. 

You should be able to measure the deflection when the wind is blowing by taking diagonals from the internal corners to set points, say the middle of the large panels front and back, in still air and at a windy time. A simple bit of trig will give you how much the centre of the panels move in or out. Measure from the internal corners because they are likely the stiffest locations in the structure as it stands, incomplete.
Alternatively use a strong but light and thin line, like fishing line, taught across the face of the panel and measure directly.

This bending is termed deflection in structures books and there are accepted limits. 1/360 of the span for elements with finishes like plaster to avoid unsightly cracking and 1/240 of the span for elements without finishes or those not likely to show damage are often used. As you know a piece of timber will deflect far beyond these limits without failing but if say the roof sagged noticeably the occupant would probably be quite concerned. Deflection becomes functionally important in flat roofs with small falls as too much leads to ponding and the weight of water in the pond increases the load causing more deflection and a bigger pond.

3. Completion of the outer cladding and inner lining will stiffen the wall panels. How much depends upon what materials and how they are fixed. Anything stiff and reasonably strong fixed in a way that avoids over stressing the material at the fixing points will add stiffness. So plasterboard may be ok although I might have personal misgivings about the fixings around the edges simply because it is easy to damage with a hammer. If the paper face is torn and the plaster cracked much of the strength at that fixing point is lost. OSB or ply is tougher and less prone to damage. 

Think in terms of paper engineering. A single sheet of paper is flexible but a sheet of cardboard made of 2 flat sheets with a corrugated sheet between and all bonded together is quite stiff and strong.

One problem you may encounter if your carcasing was very wet is the opening up of butt joints as the timber dries out. Take a stud to sole plate junction, they are held in a position relative to each other established when the OSB was fixed. If the timber dries out the sole plate will shrink away from the bottom of the stud to leave a small gap. The OSB is now potentially a hinge, albeit a very stiff one, when wind loads are applied. Rather than bend the OSB might slightly rotate about the top edge of the sole plate and slightly withdraw the nails holding the OSB to the sole plate. With an inner lining in place this possible movement is resisted and the wall immediately feels stiffer.

4. If I understand correctly fixing screws are at 24” or 600mm centres, that is too little. The TRADA Technology publication “Timber frame construction” says:

“Plywood, OSB, mediumboard, and hardboard sheathing is normally fixed to
the stud framing by nailing at 150 mm centres along board perimeters and
at 300 mm centres to intermediate studs with corrosion resistant nails
approximately 50 mm in length.”

It’s the frequency of nailing that is important, The Canadian site I referred to in an earlier post has a guide which shows how the resistance to racking can be increased substantially (over 200% IIRC) by close nailing at 50mm centres around the edges.

5. The lack of any roof bracing leaves the top of the walls unrestrained except where you have put in some temporary braces. Subjectively judging the stiffness of the incomplete wall panels without the support of a roof structure could be unreasonable. Once a roof panel is erected and adequately fixed to the walls it will improve their stiffness by three means. First the head of the wall will be held to a straight line by a structure with a much greater resistance to horizontal loads than your incomplete wall panel. Secondly the wall panel will become a two way spanning structure. Thirdly if the wall head and sole plate are well fixed to the floor and roof the studs become columns fixed in position and direction which have a greater resistance to bending than an unrestrained column. 

Continuing the paper or rather cardboard analogy an open cardboard box can be flexed quite easily and won’t carry much load. A closed box taped along the centre joint in the lid is quite strong and if all the joints are taped stronger still.

While we are on the roof is it a shallow mono pitch falling to the rear? Are the purlins running the longer way? If so do they have to?

*Summary*: Before making any judgements I would add some proper triangulated bracing in the roof plane to support the wall heads in their correct positions until the roof is erected then establish how much deflection occurs and how it compares to the accepted limits. I also wouldn’t economise on fixings, connectors and holding down or restraint straps at this stage as structural integrity is essential to resist wind damage. There needs to be continuity from the roof deck through the walls and floor to the foundations so any lifting force is passed down to and resisted by the ground.

Sorry this is so long.


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## Markymark

Graham

Thanks for the reply and compliments.

The outer OSB sheathing is nailed using Galvanised ring shank 75mm nails at 150mm spacing.

The roof is going to be a 20 degree dual pitched roof with the gable front and back. I was going to leave the roof space open inside and so there would be no ceiling timbers. Looking at the roof design pdf you sent me my open span on the rafters would be acceptable without any bracing between the rafters. I assume the OSB boarding that I am planning on using on the roof will tie the two gable ends in to the structure giving me a said "closed box". 

I was unsure what you meant by the trada publications? Sorry for the naivety. Do I need more studs??

I will attempt to measure the wind deflection but I feel I am preparing for a 10 year wind. 2009 we were hit by 80mph winds all over the south west. I am not sure how to ensure my structure does not disappear over the hill?

Again let me thank you for all your help during this project.

Mark


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## chipchaser

Hi Mark,

I was confused because I thought you might use my numbers when answering the 5 questions but I think I have joined your answers to my questions now. The following replies are in the order of your last post:



> _OSB sheathing is nailed at 150mm spacing_



That was my question 4. Nailing at 150 mm centres is ok. If you needed to increase the resistance to racking of the panel nailing at closer centres, as close as 50mm, around the panel edges can achieve that. I would only do this if racking resistance proves to be a critical factor.



> The roof is going to be a 20 degree dual pitched roof with the gable front and back. I was going to leave the roof space open inside and so there would be no ceiling timbers









Is this sketch how it will be? I have only shown one purlin although obviously there will be more! If so, the purlins plus roof sheathing and ceiling lining together can make an adequate tie between the gables provided all the roof elements are the correct size and spacing etc. and fixed together soundly.

I was thrown by your photos because there were no gable ends, that’s why I asked about a shallow mono pitch falling to the rear. I would have extended the wall studs up into the gable frames from the walls below to avoid a joint between gable panels and walls which could be a weak point



> I was unsure what you meant by the trada publications?



I read item 3 of your post of March 19th


> The centres are 2'.


 as a response to my question 4 about nailing centres. My “TRADA” quote doesn’t relate to stud centres, its all about nailing the sheathing to the frame.



> I will attempt to measure the wind deflection…



We are coming out of the windy weather now so you may not get the chance to measure the deflection under the strongest wind events until the autumn or beyond. However, I don’t believe measurement would prove much until either the roof is in place or you put in good strong temporary bracing in lieu of the roof. To give you some numbers for how wind varies through the year and where it blows from see the average wind data and wind rose at the bottom of this web page:
http://www.metoffice.gov.uk/climate/uk/sw/print.html



> I am not sure how to ensure my structure does not disappear over the hill?



If you were inland in a normal location you wouldn’t need to worry as your structure is potentially much stronger than most timber garden buildings but I share your concern about 80mph winds. Being close to the sea and in the south west of the country puts you in a higher risk category. If you are also near the top of a hill your exposure and risk is much increased. Is your site location something like this?






There is some information in part A, Section 2C of the building Regulations which is generally informative (wind speed map and diargrams page 18) but only gives answers for small masonry structures so will not give you an answer for your timber frame.

The comments I made on March 3rd still stand. If you can’t find some existing local timber buildings in equally exposed positions which have withstood wind loads to emulate you may have to pay someone like a structural engineer to check your proposal by calculation.

It appears you have neighbours close by so if a bit of the building did take off there could be damage to persons or property which could cost you a fortune. 

On the positive side while there is no internal lining or floor boarding in place it would not be difficult to reinforce the structure if that were needed.

Graham


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## Markymark

Graham

I have opted for traditional roof construction with rafters instead of purlins and a ridge board. I used the councils roofing tables to find the timber size and type. The gables are correct in your drawing.

The layout plan is similar. We are quite well protected by trees. The shed is been built in a small copse with a number of trees around. So even though it is elevated and has quite a view it is surrounded by trees. To the south west there is a lot of houses and very large trees. The only exposed elevation is the front elevation which is north west.

Lets assume I wanted to over engineer the structure to cover most eventualities except tornado alley. What additions would you recommend to my structure?

Hope I can repay all your help in the future.

Mark


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## chipchaser

Hi Mark, 

info about your site and exposure is reassuring.

When you say rafters and ridge board will you have ceiling joists spanning from wall to wall parallel to the rafters?

Graham


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## chipchaser

Hi Mark,

Info to help you choose a roof structure.





















I would avoid the couple roof (7.4c) for anything but the smallest low value structure.

I would also avoid collar roofs unless you are driven to it by lack of headroom.

Graham


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## Markymark

Hi Graham

No problem with headroom. The open span of the rafters is 2.7m or thereabouts.

Putting ceiling joists in would make a clean but rather box like design and I keep adding to my already stretched budget. The wood yard charges a premium for timber over 4.8m. Saying all that it the difference between doing it right or not. Another issue for me to consider is that the close coupled (e) would require ceiling timbers of a span of 5190mm which I would assume would need additional vertical support in the middle?

Also with a cold roof space I am assuming I would need to ventilate it using soffit ventilation??

Could I get away with one ceiling joist (Restraint) every other rafter??

Mark


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## chipchaser

Hi Mark,

I saw you were ok with headroom, it was a general comment about collar roofs.

I understand what you say about budget as your first post called for a 10’ x 14’ garden office but it is now near 60% bigger on plan  

Have you decided what the roof finish will be? Your final design can be adjusted to carry whatever you decide to use but I have assumed that you will use 18mm sheathing covered with felt which would come in below 0.5kN/sm

You could put in ties without a ceiling. Ties could be smaller as they don’t have to carry the weight of a ceiling but would need hangers to stop them from sagging. Ties could be tension wires although if you bought the smart looking stuff and its hardware it would cost much more than timber. 

You could consider using common rafters with purlin support at the centre of each slope plus a purlin as the ridge. Table A6 in Part A of the Building Regs 1992 (now withdrawn) doesn’t stretch to a 4m span purlin but by a bit of extrapolation I expect a 300 x 63mm purlin should be ok. You would need about 8 pairs of rafters (38 x 89 is the smallest in table A5 but you would probably be ok with 50 x 75) plus the 3 purlins. Because the purlins are long they should be braced to prevent winding. Add 2 more 2.7m lengths to cut for solid bracing between purlins. The purlins would be built into the gable end framing set vertically and the rafters birdsmouthed to the purlins and wall head.

However if you were willing to consider this scheme why not use 9 purlins to support the roof sheathing directly without any rafters. Extrapolation from Table A23 of Part A of the Building Regs 1992 suggests 63 x 200 should be ok at 600mm ccs.

Neither of the above include timber to build your eaves/verge ladder frames.

As discussed earlier there probably will not be so much water vapour in a garden office as in a dwelling. However, I would vent the roof to let water vapour escape.

Hope that is some help

Graham


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## Markymark

Ok Status Update

I used a Roofing table and went for 8 Pairs of Rafters at 50 x 125 PAS Tanalised. I have cut out the birds mouths and done the plumb cut. I installed them using a 50 x 120 x 4100 Ridge Beam. All C24 I hasten to add.

As I have never installed rafters on this scale I was quite surprised to feel first hand the forces especially on the side walls. It took quite a bit of balancing to hold each rafter in place as I skew screwed each to the roof plate. 

Graham I feel I need to brace these rafters. Do you think 50 x 150 x 5100 will work? What sheathing should I use as I am going to use the rest of the Tyvek Housewrap as a breathable membrane on the roof over 18mm OSB/PLY and then fitting felt shingles. I think the shingles need fixing with 18mm hot dipped galvanised collated nails?

Thanks for the advice in the last post. We are out of sync at the moment as the missus is pushing me to get it completed for May.

I have included some updated photos below. 
















Mark


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## chipchaser

Hi Mark,

When you say brace, are the 50 x 150 x 5100 timbers to be used to tie the feet of the rafters to resist outward thrust or bracing in some other way?
If as ties, are you putting a ceiling in?

Graham


----------



## bosshogg

Hi Mark...bosshogg here...I wonder if you might need a second opinion on some matters of your build. I assure you I don't want to step on anybodies toes, so to speak, I only come upon your posts today. I am a semi retired Project Manager in the construction industry, to my credit, and have been involved timber frames for a number of years...bosshogg


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## Markymark

Hi Graham

Yes, I do mean to tie the feet of the rafters together to resist outward thrust. Do they have a ceiling spanning tables info sheet??

Hi Bosshogg - Your feedback is greatly welcomed as is all feedback. 

I feel I have created a monster, I now have the scary task of boarding the roof and assuming it is safe to climb on secure 8' x 4' 18mm OSB 3 on. Then fit a membrane and fit and nail the Felt shingles. All that when I have a fear of heights. :lol: 

On a different note I have just been to the local sawmills. I was comparing there buildings, Stables, Sheds etc. They build all of them at 16" centres. I have to say they look very substantial , I feel they need to be as they originate from making Stables and agricultural buildings. I took a look at Waney edge Douglas fir at 33p a Foot for 8"-10" Wide boards. Look Very nice!!!

Mark


----------



## bosshogg

Mark have you fixed your tie batons ( "collars" right terminology _i.e._ before climbing onto the roof


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## Markymark

Bosshogg

No Not yet. I need to calculate what size timber to use. The span is 5m. The rafters are 50 x 125 with a open span of 2.8m. I was going to use 50 x 150 C24. I agree I wont attempt climbing the roof timbers until it is fully coupled. 

Alternately I could fit the collars higher up the rafter span this would mean that I could have more attractive open roof.

Is there such a thing as ceiling joist tables???

Mark


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## bosshogg

Mark...Honestly you don't need a reference table, this only a large outhouse for which you have already stated doesn't require planning permission. The crucial thing is to build a building that you will, both be proud of and will stand against the elements for the foreseeable future - yes???
OK some pointers, obviously you take all and any advice given freely, as non binding, that is you quantify - qualify - and assess said information as a means of making up your own mind, thereby removing the onus of any liability on others, should something go wrong! I will assume your compliance unless you inform otherwise[/colour]

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OK... 600mm centres is fine, the 600 v 400 centre scenario has nothing to do with what a buildings final use is to be, but is about stud dimensions used _i.e._ 100 x50 and above 600 is fine, 75x50 or less should be 400 centres. You say you are using 125x50 Tanalised batons for the rafters, best use same for your braces (correct terminology - collars) as you have fitted the rafters you should cut the the collars the exact length (designate) between opposing walls, fix all collars one side only with five 90mm galvs, oh are you using a nail gun or a good old fashioned pelty (hammer) and swear words??? with collars all fixed down the one side only (choose which side you are going to fix them too) then match them all to the same side (comprende) get back to me if unsure, I'll do a sketch, now line up the same side wall fix a string line along the collar ends ensuring all ends line up, using a temp brace, brace this wall at in position...Now the other side...assuming you have cut the collars, all to the same length, they are now in parallel to the first side (I speak of the collars only, not the second wall per-say) nail up this side same as you did the first, only this time pull/push the wall until it lines up with the collar ends...you now have a parallel building. Cut the ends of the collars to match the angle of the rafters and nail on, with the correct twist nails, truss clips to all the collars and rafters where they intersect with the inside of the walls (the ends of these will be covered by your plasterboard lining) this ties the whole roof structure together. Now you need to tie your roof structure to your shell, to do this you need to get some hold down straps (bat straps are as typical) like this once nailed you have a monolithic stricture, in some sense which will counteract any wind lift...I'm a bit puzzled about you fitting insulation in the wall structure but wanting to retain the lofted roof space open, I assume you have some other means of insulating the roof???...bosshogg


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## chipchaser

Hi Mark,

Good to see that you are pressing on but before fixing your roof deck you should, as bosshogg says, ensure that the rafters are tied. The roof structure as a whole must be adequately tied and braced so that all the components are in their correct positions and acting together to make a stiff and safe platform to work on. You may need temporary props and battens pinned to your rafters. I would stagger the end joints of your sheathing so they are not all in line.

Do have in mind that once the roof is on and closed your structure will be subject to the full wind loading. I would make sure that you are satisfied with all the following:

Ties to the foundations to resist wind loads
Solid connections between the floor and the wall panels. The minimum I would look for is a bolted connection at centre and each end of each panel plus a bolted connection at either side of the door opening.
Solid connections between adjacent panels at each corner close to the top and bottom of the panels plus one near the centre as a minimum.
Good bolted connections between the front and back wall panels and their separate gable panels.
All bolted connections should have large washers both sides, I would use large square plate washers.
Pressed metal plate connectors to strengthen and stiffen the connections between roof structure components, see below.
I am sure you have all this covered and hope you don’t mind me reminding you.

Back to your questions;

Fixing of your shingles should be as the maker’s instructions. As far as I know “collated nails” are used in nail guns, ok if you have one but loose nails would do the same. Never used felt shingles but plain felt fixing is usually with galvanised “clout” i.e. large headed nails.

There are tables showing ceiling joist spans in the old archived version of the Building Regs Part A which can be downloaded free at: http://www.planningportal.gov.uk/upload ... A_1992.pdf See tables A3 & 4. Remember that all these tables are for buildings that fall under the control of building regs and the sizes will be calculated to restrict deflection to 1/360th of the span. If you are happy to accept more deflection you may be able to reduce the timber sections.

I would not have used rafters on this roof without purlins and birdsmouthed connections at all rafter supports. Working from where you are now I would add hangers to minimise the deflection of the ties/ceiling joists and I would add binders to stiffen the structure, to add some lateral support in the short direction of the building and to prevent winding of the ties. Before you fix the hangers temporarily prop or lift the ties so that the deflection is taken out. You can then add the binder(s) across the top of the ties making sure they are well fixed to the walls at the ends.

I would use pressed metal plates to add strength to the timber connections. They are easily found at decent builder’s merchants. You can see the sort of things at:
http://www.allmat-online.co.uk/download ... alwork.pdf
http://www.batmetalwork.com/bat.pdf
http://www.strongtie.co.uk/catalogue/Straps.pdf

Through nailing or screwing can be ok although it may not provide as strong a connection as metal plates and is prone to split the timber especially at ends of small sections. If the timber is split the strength of connection is lost. Metal plates rely on the use of many smaller nails, commonly square twisted nails, or suitable screws or bolts where appropriate.

Using common rafters on your shallow pitch roof means there will be a lot of outward thrust at the rafter feet. You will need to connect the ties securely to the rafter feet and the head of the wall. I looked up the safe load on a 12mm bolt in 47mm timber and found you would need three at each end. The bolt holes should be a snug fit, not oversized, and the washers (two per bolt) diameter 3 times the bolt diameter. Bolt holes should be 7 diameters from the end and 4 diameters from the side of the members. Toothed timber connectors would increase the load carrying ability of the connection but I don’t have any figures for them. I would consider adding them between the timbers but they do need pressing in to place. Just tightening up the bolt can overstress the threads. You can fit them to low density softwood without the correct tools by using strong G clamps to squeeze the timbers together whilst doing up the bolts, equal pressure on each as you gently tighten the bolt. You may think they are not worth the trouble.

As before you should temporarily take out the deflection in the tie before making the fixings at the ends.

Raised collars will not resist the outward thrust of the rafters. For your span and low pitch I would have looked at purlins or engineered trusses. Purlins would have given you an open roof. Maybe you could redesign your roof to support the rafters by purlins.

What size timbers were they using in the stables etc at your local sawmills? The ones I am familiar with use ex 3” x 2” planed softwood at 24” ccs. The roof purlins of the newer ones are 6” x 2” sawn whereas the older boxes (at least40, probably 50 years old) have ex 3” x 2” purlins at graduated centres: 36” – 24” – 12” top to bottom. The old ones have t&g boarding covered with onduline on the roof. Both buildings are adequate for their uses and don’t show obvious signs of failure but they are significantly smaller than your garden office, 3.1m square for the older ones and 3.1 x 3.7 for the newer ones. 

Keeping a simple rule of thumb in mind may be helpful, stress generally increases as the square of the span so if you make your span 25% bigger the stress will increase by 1.25 x 1.25, that is 1.56 times more stress. The same applies to wind loading so a small increase in basic wind speed due to proximity to the coast and being in an elevated country location can make a significant increase in stress, e.g. 50% higher basic wind speed works out as 1.5 x 1.5 = 2.25 times the stress.

I am not trying to make this more complicated only pointing you to all the information you need to make your decisions. When you have a windy day your shed walls, floor and roof need to work together as each element on its own is not particularly stiff in all directions. Imagine the front panel standing on its own, not much wind would be needed to blow it over. So wind load on the front panel needs to be transferred or “shared” with the side walls and the roof. At 50mph the wind load on your walls could be 1.8 tonnes horizontally and 1.2 tonnes of lift on the roof. The mass alone of your shed is probably a bit less than is required to resist this so you do need these good connections from foundation to roof which I commented on at the start of this post.

As an aside, to see a failure in wind is really scary. A few years ago we had a site with a temporary roof up in December. One night about six roof sheets blew off and landed in the car park the other side of the road from the site :shock: . Fortunately the loss of those few sheets allowed the wind to blow through relieving the load on the rest and very much more fortunately the pre Christmas party had ended a few hours earlier and the car park was empty.

PS just seen what bosshogg wrote today and agree with what he said. Apologies for any duplication. The building is simple and will be trouble free if you do it right. There are some important principles in building that are not obvious until someone tells you about them. When you start a project with not so much prior knowledge there is a lot to pick up quickly so I do admire what you have achieved and how you have pressed on.

Graham


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## bosshogg

Mark...I have just read Graham's latest post...all good advice...we appear to be on the same track...now looking at the photos you posted and referring back in posts, I think you expressed a wish to have eaves extending all round the building your front/back eaves effectively achieve this trough their projection from the shell. Also in the photos the gable walls are terminated with a header (stud on it's side) can I ask if these are in line with the bottom of the rafters to allow ladders (frames built same height as rafters, but built from say 125x32mm Tanalised - 125 being the width of the batons you used for the rafters) to be built and fitted to extend the roof projection past the gable walls (as per the front and back elevations)...bosshogg


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## Markymark

Thanks Both Graham and Bosshogg

Great information from some very experienced people is valuable to us Novices.

Bosshogg - I feel I understand. I have looked at where the plumb line of the rafter intersects with ridge board and some of the rafters look about 10mm too short. This formas a pattern as I have not fixed the rafters to the ridge board yet. When I look at the rafters on one side the ones closest to the gable are fine but the rafters increse their gap as they reach the centre of the ridge and so I have deduced, as they were all produced with the same pattern rafter that the centre of the side wall is deflecting by 10mm which would not be hard at all.

I have decided to use a ratchet cramps to remove this deflection in the side wall and so close up the connection betwwen the rafter ends and the ridge. At this point I shall attach the said Ties (Ceiling Joists) to one end of the rafter where it intersects with the roof plate. 

I WAS insulating between the timber fram using celotex or the like but that was when I planned to have a open dual pitched roof. Now I am needing to put a ceiling in I will insulate the roof void with rockwool and ventilate as required.

Points I am not sure on is the use of fixings to the end of each tie to attach it to the rafter. Should I use bolts or Nails?
Or possibly a bit of both.

Should the timber for the 5M Span between the two rafters be the same as the rafters? If so will it not sag in the middle and if so sould I use some kind of timber brace between the rafter and the ceiling joists?

When you say tie the roof structure down to the wall frames using straps. Do you mean the twisted galvanized straps to hold the roof on to the wall framing?

On the theory of this. If the ridge board is freely supported by the gables and the rafters attached to this ridge board, would that not remove the outward force that pushes the walls outwards?? Would it not be like taping two playing cards together and lifting them in the middle with say a pencil of pen??? If you lift high enough the cards come together.

I am learning off the cuff at the moment. Its a great process and I feel I would be lost without your help.

Graham - With the above comments also. I feel I should invest in some Coach bolts. At the moment the structure is held together with 6" screws top middle and bottom. Where the walls intersect I placed three 50 x 100 studs and so it would be difficult to keep a bolt within the stucture.

Apologies if I have not covered eveyhing here but I feel a little on the information overload. I feel I need to read your valuable posts again to soak up all that they contain.

Again Thanks for all this great help. Yes in this crazy world it pays to ensure that the advice given is given without and obligation. 
If the structure collapses it will be only me to blame hence why this information is so valuable.

Please dont ever feel that you should not share your great experince with others for risk of legal liablity this I feel would silence great forums like this.


Kind REgards

Mark Howarth

PS BossHogg do I need to keep calling you Bosshogg or just Boss. :lol:


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## Markymark

bosshogg":3vhl8w74 said:


> Mark...I have just read Graham's latest post...all good advice...we appear to be on the same track...now looking at the photos you posted and referring back in posts, I think you expressed a wish to have eaves extending all round the building your front/back eaves effectively achieve this trough their projection from the shell. Also in the photos the gable walls are terminated with a header (stud on it's side) can I ask if these are in line with the bottom of the rafters to allow ladders (frames built same height as rafters, but built from say 125x32mm Tanalised - 125 being the width of the batons you used for the rafters) to be built and fitted to extend the roof projection past the gable walls (as per the front and back elevations)...bosshogg




Due to my lack of experience I designed the Gable frames in four parts and used a post in the centre to support the ridge beam. In doing this the roofing calcs made the end of the timber flush with the end of the front and rear walls. I was not aware at the time that this would be lower than the Rafters as they are only partially sitting on the edge with a birds mouth. The difference is not a full rafter size but the projected line from the top of the birds mouth and the end of the rafter or less I assume it is. I am not sure if that give enough play to let me make a small ladder frame??

P.S. I am using a Nail gun with 90mm ring shanked nails Galvaniszed of course. (hammer) 

Mark


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## bosshogg

Mark I'm going to answer your points one at a time as I read them, some I may ask for some clarity should I not quite understand...OK...first rafter alignment, I was trying to ascertain the alignment of your rafters to the gabled (angled) head plates of four gable frames..._i.e._ if you placed a straight edge across the rafters and overshoot the gable frames, would the rafters be above the frame by 125mm (upper 50mm edge of rafters) leaving a 125mm dimension, in which to lay your ladder extensions...bosshogg


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## Markymark

Bosshogg - No the top of the rafter is about 84mm above the gable wall. I was thinking of making a small ladder frame. Do you think that is possible??

Mark


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## bosshogg

Mark normally the ladders would be built out of 100x50mm nominal CLS (Canadian lumber supplies) a nominal dimension for what the batons are dressed from, the finished size is about 76x 38mm, CLS is that planed all round (PAR) with round edges you see at the timber merchants, and is generally the timber of choice for kit manufacturers, probably because they get a good deal from the importers, also being both PAR and rounded corners means fewer skelfs (Scottish slang) in kit joiners fingers, less absenteeism (homer) anyway this might still allow you to construct you ladders, they cantilever over the gable frames and are fixed (scew nailed) to the gable top runners and spiked to the rafters (affixed/nailed with 90mm nails) have a look at this and see if you understand 



I think communication lines are getting crossed at times, could we figure out how to resolve this?...bosshogg


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## bosshogg

The handle boss comes about because I was the boss for such a long time. Site Manager, Project Manager, leading hand joiner, whatever it stuck. Hogg is my surname put the two together...bosshogg...famous/infamous character/caricature from the "Dukes of Hazard" now there was a program...you can call me whatever you like, as you can see from the above the guys on site did...my first name is actually Allan...cheers


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## Markymark

Thanks for the additional input. 

I have taken a look at Building controls Ceiling tables and ceiling joists at 5m clear span and 600 centres would require some big timber. 50 x 220 seems to ring a bell. I cant help feeling that this is the wrong way to go as 8 ceiling joists at this size would be a lot of wood. When reading the tables it seems as clear as mud and so I am not aware if fitting vertical timber struts (not sure of technical words) between the rafter and the ceiling joists would allow me to reduce that section size some what?

My other option as Graham put it was to intoduce two rather large pulins with birds mouths cut in to them and fit them on either side at the half span point of the rafters. This I would have problems with the connection to the gables. I do feel I have to look at this if option a is seven 220 x 50 x 5000 ceiling joists.

I would be grateful if we could explore these options to see which one is more viable, less work and less cost.

Thaks again for all the additional help. 

Mark


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## chipchaser

Hi Mark,

re smaller ties see previous post, last sentence of this para:

There are tables showing ceiling joist spans in the old archived version of the Building Regs Part A which can be downloaded free at: http://www.planningportal.gov.uk/upload ... A_1992.pdf See tables A3 & 4. Remember that all these tables are for buildings that fall under the control of building regs and the sizes will be calculated to restrict deflection to 1/360th of the span. *If you are happy to accept more deflection you may be able to reduce the timber sections.*

Graham


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## Markymark

chipchaser":2734mwr7 said:


> Hi Mark,
> 
> re smaller ties see previous post, last sentence of this para:
> 
> There are tables showing ceiling joist spans in the old archived version of the Building Regs Part A which can be downloaded free at: http://www.planningportal.gov.uk/upload ... A_1992.pdf See tables A3 & 4. Remember that all these tables are for buildings that fall under the control of building regs and the sizes will be calculated to restrict deflection to 1/360th of the span. *If you are happy to accept more deflection you may be able to reduce the timber sections.*
> 
> Graham



Thanks Graham

I did take a look, the ceiling joists they were recommending were, I think, 50 x 220 x 5000 I really am lost at the moment. Luckily the weather has turned so even if I wanted to I could not progress. I am interested in your Purlin idea. I will be honest your initial idea of a purlined roof seemed great but I could not get my head around making the gables for them to sit on. The problem is I have a view in my head and not a lot on paper. When it came to it I could not think how I was going to transfer all the weight of the purlins to the main structure evenly. I could not picture how to create a smaller gable to sit the purlins on. Then I had a thought!!! I remember you saying this way it would avoid me having to cut all these birdsmouths and I thought I was taking your advise to make life easy. I am after all very interested in woodworking and could do to learn through doing so I decided to go for all the rafters, which i have to say I enjoyed!!

You mentioned if I put two Purlins, one on either side of the roof I could do without the ceiling joists?? I am interested in that option. I would like to compare all my options and as you say "do it right".

Please could you expand on these concepts.

Mark


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## chipchaser

Hi Mark,

It was windy today in Northants, I struggled to open my car door just as R4 was warning of 50mph winds. If it was like that in Devon, not a day for clambering over your roof with an 8’ x 4’ sheet of plywood.

Ceiling joists: If you accept more deflection, make your ceiling as light as possible and of material that won’t show cracks you can minimise the section of the timber tie. A T&G matchboard ceiling looks good in a “cabin” is comparatively light and any movement is accommodated by the numerous joints between the planks. On the other hand, due to all the joints it does not provide the racking resistance that a sheet ceiling would. So maybe plywood panels with cover strips at the joints would be better if acceptable to you aesthetically.

Bosshogg suggested a smaller tie than shown in the tables. Timber is quite good in tension as long as the area available for fixing is adequate. What I mean is that sometimes the local stresses around the nails or bolts at each end dictate the size of the member. In your building 220 x 50 is more than you need. 

I think I posted the book extract comparing roof structures after you had decided to go with rafters. Had you seen that earlier and chosen an all purlin roof, as the BR Part A table for purlins supporting sheeting, you could have made a stressed skin panel for each roof slope, ply sheathed both sides, strong, light and simple.

I think you must now decide what you want and stick to one track. It will be simpler for you to follow bosshogg’s directions to complete your roof and you will have the benefit of his experience to guide and reassure you. 

If you really have to have an open roof free of ties and hangers etc it will cost you in time plus the additional materials. In outline, one way to do this would be as follows:

I note what you say about providing support for the purlin ends at the gables. With this in mind I suggest that if you really want to pursue this idea you adopt two purlins per slope located so they are as near as possible equally spaced whilst falling above a section of solid wall, that is, not above a door or window opening.

Place the purlins vertically and use short studs within the gable panels to prop and contain the purlin ends. It’s like forming a box around the end of the purlin so it is held in place and can’t wind (twist). If you cut away the ply face the purlins can pass through and project to form the principal supports for your verge ladders. To set out the purlin positions you would first mark the line of the underside of your rafters on the gable ends. Then set the outer top corner of each purlin so that it does not cut into the rafter beyond 1/3rd of the rafter’s depth whilst providing not less than 50mm horizontal bearing for the birdsmouth.

Below the new purlin locations you would need to ensure enough support to spread the loads into the wall frame and down into the floor perimeter beams and thus to the foundations. That’s not as hard as I have made it sound, just add studs below the load so there is a vertical load path to the floor perimeter beam.

I would replace your ridge board with a proper purlin. However, because you have already cut your rafters to lie against the existing ridge board I would lift the ridge purlin and plant (glue and screw) timber ledgers to provide a bearing for birdsmouths at the top of the rafters. Now you can re-use your existing rafters by cutting them to fit.

Don’t forget that as your purlins are long (relatively in structural terms) they need to be restrained to prevent winding (twisting). You could put solid blocking between the purlins after you have fixed your ceiling. I assume that you will part fill the rafter depth with insulation and pin a ply, or whatever, ceiling to the underside of the rafters between the purlins.

Re your comment that you had little down on paper: I find it really does help to sketch out what you want to do. The process of drawing makes you think about how parts come together and generally shows up potential problems. Quick freehand sketches are all you need to work out the basics. CAD, Sketchup etc are good for the later stages when you need to put dimensions on parts but you can be trapped in the process of drawing which kills spontaneity. A quick sketch has little penalty of time attached so you can screw it up and do another without feeling bad.

I hope this answers your question and give you more to think about. 

I am sorry to say that I cannot spend any more time on this as I have work to progress and need to devote all my time to it whilst the weather is ok.

Graham


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## Markymark

Thanks for all your Help and support in this project Graham.

Your feedback has always been concise and very invaluable. I hope your project goes well and wish you all the best for the future.

I'll post photos of the completed project. 


Kind Regards

Mark


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## Markymark

Okay and now to compare my options.

Bosshogg - You kindly mentioned that I use the same cross section of timber I used for the rafters for the ceiling joists (Collars). I am a little confused with how I attach the Truss clips and Bat straps. Sadly the pictures did not show on your post but I did a google search and I think I found some.





Is this what you mean for connecting the roof structure to the studs? If so do I need one on each rafter/collar combination on eiter side?







Is this what you mean for the truss clips? You say to fit them on the inside of the building? I assume you mean connecting the collar to the roof plate? Apologies for the question Is that not what the bat straps do?? Or Have I attached the wrong type of bat strap to the post??

My Rafters are currently Skew Screwed at the wall frame. I pilot drilled holes from the centre of the seat cut and exited from each side. 

Apologies for all the questions you are dealing with a complete novice.

Mark


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## Dibs-h

Mark

Can you post some more picture from the inside of your wall construction? One of each wall would be fine. 

I would also suggest you stop for a moment and have a serious think about the type of roof construction you want and the primary constraints\considerations (i.e. headroom, cost, ease of build, etc.). Once you start building - changes direction costs both time & money.

HIH

Dibs


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## Markymark

Ok Dibs Here they are:- I put up a couple of the corner connections also.

Here is a link to all the photos on Flickr. Hope you can see them ok.

http://www.flickr.com/photos/markymark144/

Let me know.

Thanks

Mark


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## bosshogg

Hi Mark...for a complete novice you've certainly progressed to a remarkable and competent state so far. From the pics you've posted what you have is, as far as I can tell, is a rectangular structure which spans from the two side elevations 5m wall to wall.

What I advise you do now is work with what you have, any radical changes at this juncture will likely be costly and hamper your time frame for completion. To that end I will sketch a stick built (not pre manufactured) truss layout which embraces all you've accomplished so far...hope you can come along for the ride, as it will be fast and precise!






The rafters are your originals, birds-mouthed over the wall plates, the collars are raised (your decision, but be mindful of standard plasterboard sizes i.e. what you can get off the shelf) for all things plasterboard you can generally get most of your answers from here http://www.british-gypsum.com/pdf/S... but hopefully it will be worth it...bosshogg


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## Dibs-h

Mark

Cheers for the pictures. Walls - I would have used (and did use) a 4"x3" wall plate to sit the rafters on. The walls where there is a door and windows, I would have doubled up the header above those, especially for the door, where in one of your pictures, there is the "post" coming straight down onto the door header. That would transfer the load straight down to the doorway header.

As for the Kingpost's - Bosshog, I'd be inclined to disagree, if as your post reads to me that all the trusses are to be KP ones. There's been plenty of shed's built with simple trusses, either using bolted connections or ply plates over the connections. King post trusses is overkill.

Mark - I'd pause it and get some professional advice. Needn't pay for it, but a roof isn't like a stud wall, which might sag, etc. but a roof (poorly designed) could come crashing down a lot easier and probably collapse the building. 5mx5m isn't like 6'x6' shed storing the lawnmower and stuff.

It's a shame Mike Garmham isn't about on this forum - having said that you may want to post up on www.thewoodhaven.co.uk where he is active.

Dibs

p.s. I'd have a look thru the other threads of folk who've done an all timber built & there are a few who made their own simple trusses.


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## Markymark

Boss.


Great information thanks a lot!!

Are you suggesting that I remove the ridge board and build trusses as per the diagram? I feel happy with keeping the collars on the tops of the wall and I am sure they will be strongest here. Are you suggesting that I need to make king posts and the diagonal bracing as per the diagram? 

It looks great, but it also looks like their is something inherently wrong with my roof as it is. The pitch or angle of dangle is 20 degrees so it is a low pitched roof and this is not ensure it complies with permitted development rules. Under 4M, Dual Pitched, La di da di da.....

Sorry but I am not sure what direction I am taking? I was thinking of leaving the rafters as they are and placing two struts?? one halfway up each rafter and connecting them to the collars to make a similar shape as in a loft truss. I was not thinking of taking out the ridge beam and replacing it with a King beam. 

Do you think my way is possible or am i only dreaming. 

With regards to wind direction Graham , on an earlier post put up a drawing of the site layout with regards to North south east and west. As we are about 3 miles as the crow flies off the south coast I assumed the prevaling wind is a South westerley. All elevations have heavey woodland around except the westerly elevation which has a gorgeous view over the blackdown hills. This elevation is inherently weak as it is the large 1200 opening for the double upvc french door and two small 620 x 820 windows. Looking at the front elevation and notbeing astructural engineer ||I would say the wind would blow up the hill on the westerley face and wont to lift the building off its piers. To address this I was going to frame out the underside of the structure to keep wind from blowing under the floor and wanting to lift the structure which is I may add bolted to each corner pier with M6 Bolts. This is another story but I just feel you should know my feelings on this. Ok back to the roof.....

I'll await your confirmation on what you feel is the best and most cost effective way to proceed with my roof.

Thanks again

Mark


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## Markymark

Thanks Dibs - Not sure if I'm any further forward. 

Cant see the wood for the trees.....


I am aware I need to get this baby watertight as the wet weather keeps showing its ugly head and even though I have used OSB 3 it is only water resistant. 

Thaks for the input though.


Mark


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## bosshogg

Mark...update to your latest post...keep the ridge boards I wasn't thinking when I posted the sketch, this was an indicative sketch I adapted to show a basic layout that would address all of the issues you had raised from previous posts. Forgive me if I have presumed to much, but so many variations appear to have come and gone it is not apparent the definitive state of play that's current, please don't take that as any form of criticism, just clarity...now that you state your happy with the ceiling at wall head height omit the raised collars (in sketch) from your mind and go back to my earlier post detailing how both to cut the collars to the predetermined shell width (measure on site the width between gable panels both sides - if you've done your job right, as I'm sure you have, both gable elevations will be the same) cut collars to suit the rafters ensuring that they are all identical i.e cut one as a template, choose one of the outermost pair of rafters to measure/fit it, when fitting the others push/pull your shell walls to achieve a snug fit for each one (you will probably require assistance for this) cut and fix the struts, my best advice, *as you see above*. The idea behind this elaborate advice is that this should allow you to plumb and straighten your structure with minimum confusion and re-measures...you can omit the king posts at your discretion, however I would advise you to double up the struts, something like this 


the idea of any truss design is to best distribute the load that the completed roof structure will apply to the shell and to minimise movement in such a light structure. That being said the timber you have chosen for your roof is sufficiently heavy allowing you to take liberties at your discretion. Truss clips and hold down straps should be as per my last post (you may have to source singles and fit one either side of the truss and gusset assembly at the wallhead although if you find any with the right space to suit your assembly, all to the good) your 20 degree slope will work fine with this strut configuration and as far as I can see the current rafter layout is fine...unless anyone else can see fault?...sorry I didn't take time to review Graham's earlier post re the setting and location of your structure, now that you have pointed it out, the ridge board will provide one brace and if you could add say 3 more (nail them to the struts, wherever convenient bearing in mind you want to achieve go wind load distribution)...re the tying down of the shell to the foundation piers, this can be achieved with straight hold down straps fixed to the outside of the Tyvek following a stud line down to the piers...hopefully this answers all your queries...bosshogg


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## Markymark

Bosshogg

On the original post you mentioned that I layed the collars to the side of the rafters but in your illustration they are mitred in front. 4

Sorry for the confusion. 

Mark


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## bosshogg

Mark...no need to apologise, I'm getting a little confused my self...as long as you feel you can plumb & straighten one external wall (not gable wall of course) I'd chose to cut the angles and squeeze in the collars under the voids between the 20 degree angle and the wall plates, with the first side fully nailed up snug, the opposite wall can be free to push/pull to fit the collars at that side in, and assuming you can cut all collars exactly the same this will self straighten the opposite wall, I hope you can understand all this. Once all is fitted and nailed (nails punched in flush) you can glue and screw the gussets, as per the last diagram. I took this truss design from one of my old contracts and it work very well, tried and trusted, you could say. Once the clips, straps and wind bracing is affixed you should have a good structure. When the walls are strapped to the piers your shell should be solid and ready for the roof covering( I assume you have worked to metric dims therefore you should get metric 11mm boards 2400x1200x11mm they are available)...bosshogg


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## Markymark

Boss

You say nail them and then fit them inline with the rafters and then fit the gussets. Before I fit the gussets where should i nail the two sections?

My only concern is that on trusses they are not usually Birdmouthed. Will this not cause a problem making the connection between the rafters and the collars?

Am I orderering 50 x 125 x 5000 untreated c24 timber or 50 x 150x 5000 untreated??

Finally Can I install the diagnal struts vertically at the halfway point between the rafters on either side? This will mean I can use the loft space for storage!!

I feel my mind is moving somewhere now...thanks.

Mark


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## Dibs-h

Markymark":28jfes2t said:


> Boss.
> 
> With regards to wind direction Graham , on an earlier post put up a drawing of the site layout with regards to North south east and west. As we are about 3 miles as the crow flies off the south coast I assumed the prevaling wind is a South westerley. All elevations have heavey woodland around except the westerly elevation which has a gorgeous view over the blackdown hills. This elevation is inherently weak as it is the large 1200 opening for the double upvc french door and two small 620 x 820 windows. Looking at the front elevation and notbeing astructural engineer ||I would say the wind would blow up the hill on the westerley face and wont to lift the building off its piers.
> 
> Mark



Mark

Wind doesn't just load a building in the traditional sense - i.e. blow against it. It also creates a suction affect which can and does affect a building to a lesser or greater degree.

In your above post - assuming the trees shield the building, the movement of air above your building horizontally will create a suction affect on your roof and needs to be taken into account.

The openings in a wall weaken the ability of a structure to resist wind loads.

*I will re-iterate what I have said before* - you need to stop and pause for thought. Rectify the framing issues in your walls and then work on and finalise a design for your roof. Not only taking into wind loading (and suction), but taking into account what you can fabricate and what you can't. It may be better to buy pre-made trusses at this stage. These needn't be prohibitive in terms of cost. I had trusses costed for a 4m wide and 6m long garage quoted at £600 and it was marginally more than I could have had the timber supplied for. If you are unable to take wind\snow loading into account - have someone else do it.

Regards

Dibs


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## Markymark

Dibs

Thanks for your advice. As a trained pilot I am totally aware of wind loading on structures. I am not sure what framing issues you are talking about? I can only assume you mean the header above the door as per your last post. 
If I could ask you to be more specific I can adopt your feedback. Making accurate trusses is childs play with the help of other more experienced forum users and as this project is for self gratification I could not farm out any part of it. This project is about learning through doing not taking the easy route of buying in.

Please dont take this the wrong way but I only work with a positive mental atitude and if I wanted to save money and time I would have bought a Kit cabin. 

This thread has been runing for quite some time now and so far it has been very creative and has presented me with answers to possible problems that may arise. 

I welcome your positive and constructive criticism and hope you can share your years of experience.




Kind Regards

Mark


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## Dibs-h

Mark

Obviously we aren't discussing aerofoil design here, as you don't want your building lifting off.

Framing issues - over your openings you are missing the doubled up headers. The wall plate where your rafters sit are undersized. Are the nailing patterns for the studs, noggins, etc. as per TRADA's recommendations? Have you cut birdmouth's in the ends of your rafters? What is the depth of the vertical cut of the birdsmouth as a ratio of the rafter depth? Have you skew nailed them from both sides?

"Using a ratchet strap to close up the gap where the rafters meet the ridge board" - it appears the length of the rafters is marginally short. How well do you think the fixings will cope with the tension that will be created once you release the straps and over time under the tension?

How do you propose to contain the outward thrust at the base of the rafters? What's the depth and thickness of your ridge board?

Having created 3 openings in one wall - a set of french doors (IIRC from one of your earlier posts) what negative affect does that create in terms of wind loading? How do you propose to deal with that? In my own build putting 3 openings in a masonry wall caused the structure to fail wind load calculations with a traditional purlin and rafter roof, until the design was modified to include 2 large King Post trusses and their large tie beams. That's in a sheltered location compared to yours. So how is your current design going to fair - worse, comparatively speaking.

Is you nailing pattern for the OSB as per TRADA's recommendations, in terms of nailing pattern\density and nail spec?

What are your primary requirements from a roof? Ease of build? Headroom? Cost? Aesthetics? As these will dictate the options you have to choose from.

As for taking your comments the wrong way - don't worry about that, after all it's your shed. My comments earlier regarding pausing for thoughts still stand. I appreciate you might not see it, but to me this build, i.e. planning on the hoof, isn't the best way forward. You may pull it off or you may not. You may disagree - in which case we can agree to disagree.

Regards

Dibs


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## Markymark

Thanks Dibs 

That's exactly what I need. Possibly a little bit more on how to rectify said issues. 
Positive criticism. With regards to nailing yes it is in excess of Trada's specification. I have birdmouthed all the rafters and they are skew nailed. They are bird mouthed to 1/3 of the rafter depth. As I am going to turn them in to Trusses shortly or their equivalent shortly I feel I am addressing the wind load on the roof. The roof itself is having sterling boards fitted with felt shingles or something similar so the roof has very little weight. 

The front elevation is a concern for me. but I feel some binders should provide a little support as the collars will be running the other direction. 

With regards to the rafter length they are all exactly the same length of the Pattern rafter. This leaves two options either the ridge which is 50 x 125 is not straight but then the rafters on the opposite side would be high, or the walls are deflecting under the load and that when I correct this by installing collars they should meet accurately at the ridge beam. 

I read your Workshop project and I am very impressed with your king beam trusses. This is something I would love to work on in the future. 

Apologies but I am getting a lot of pressure from her indoors regarding the build and feel I just need answers not problems so late on in the build. 

I hope I did not offend with my comments and I will attempt to address the issues you have so kindly highlighted. 

P.S. A wing is very similar to a roof, the areodynamics cause low pressure above causing the suction effect you pointed out which in a plane induces lift. :wink: 

Mark


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## Dibs-h

Markymark":2yu4ja41 said:


> ... I am getting a lot of pressure from her indoors regarding the build and feel I just need answers not problems so late on in the build.



You aren't the only one in that boat - that's day to day life for a lot of us.


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## Markymark

bosshogg":2k62bmii said:


> ( I assume you have worked to metric dims therefore you should get metric 11mm boards 2400x1200x11mm they are available)...bosshogg



I have worked to Imperial measurements because my local wood yard and Builders merchant stocked 2440 x 1220 x 11mm so I stuck to 2' centres. I have followed those centres to the roof so each rafter is sat on a stud. Should I not use 18mm Sterling Board to cover the roof as I am using felt shingles which are attached using 18mm clout nails ( I think).

Still a little unsure on the size of the timber for the lower chord (Collar).?


Mark


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## bosshogg

Mark...12mm OSB is standard dims for roofing, even atop seven story buildings, why anyone would want to manhandle 3/4" (18mm) 2'x4' sheets on a roof would puzzle :shock: me...stick with the same timber as rafters...only thing birds-mouthed rafters will do is displace the point of the rafter/collar joint inboard 20mm or so!...wouldn't advise using loft as storage loft from the headroom point of view, at present with the layout suggested you will produce some 2 meters wide along the full length of the building, provide a hatch, and store only that which is easily reachable...as far as advisory organisations go, you might want to approach your local building control office (this is not PLANNING) which you have already stated is not required. Actually I wonder, whilst you are not required to apply for planning permission, you may require to provide a building warrant, best check, if no ask for there advice, see if it comes without cost to you...bosshogg


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## Markymark

Thanks

Cembrit say that the felt shingles should be nailed in four places with 3-3.5mm Galvanised clout nails of a minimum of 22mm in length. I suppose I will have to put at least 18mm Sterling board on the roof. There is also a safety issue with climbing on 11mm OSB. I would not feel comfortable climbing on a roof whose rafters are at 2' centres and is covered with 11mm board.
http://www.cembrit.co.uk/Admin/Publ...es/Filer/uk/PDF/Shingles/Bitumen-SHINGLES.pdf


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## bosshogg

Mark…I think you’d best qualify from the felt shingle manufacturer what roof substrate they expect these shingles to be fixed too, no roof covering I’ve ever experienced would take 22mm or more clouts without penetrating through the sheet, this would mean that loft spaces would become dangerous places where peoples scalps could get cut. The only thing that I can come up with is that these are expected to be affixed to counter batons, best check…I can understand anyone new to walking on a roof sheeting of only 11mm thick, but I can assure you it is quite safe from that point of view. Health & Safety regs. would not condemn the substrate, but would expect compliance with working at height regs. a minimum of an eaves height scaffold, you won’t fall through the roof but you can fall from it!
2’centres…that leads me to another issue, I don’t know of anywhere that you can get Imperial plasterboard, in my experience you can only source metric, have you figured this out?...bosshogg


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## bosshogg

Mark…I think you’d best qualify from the felt shingle manufacturer what roof substrate they expect these shingles to be fixed too, no roof covering I’ve ever experienced would take 22mm or more clouts without penetrating through the sheet, this would mean that loft spaces would become dangerous places where peoples scalps could get cut. The only thing that I can come up with is that these are expected to be affixed to counter batons, best check…I can understand anyone new to walking on a roof sheeting of only 11mm thick, but I can assure you it is quite safe from that point of view. Health & Safety regs. would not condemn the substrate, but would expect compliance with working at height regs. a minimum of an eaves height scaffold, you won’t fall through the roof but you can fall from it!
2’centres…that leads me to another issue, I don’t know of anywhere that you can get Imperial plasterboard, in my experience you can only source metric, have you figured this out?...if you want I could send you a PM detailing the road map to truss roofing, let me know…bosshogg


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## Markymark

Hi Bosshogg

Awaiting a reply from Cembrit regarding felt shingle fixings. With regards to 2' Centres, I chose imperial due to the fact that all the sheets of OSB were 1220 x 2440 (8' x 4') With that in mind I could either have it easy on the outside or on the inside not sure why they all dont stock either imperial or metric sheet products? For additional resiliance I was going to clad the internals with either ply or some other imperial sized sheeting product.

Mark


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## bosshogg

Mark…just call me boss…no extra resilience required, if I understand your use of the word correctly [able to absorb shock/load] this is not an improvement as such. Better if you can source 40 or so 2440x1220 standard or better still duplex boards (foil backed) which provide both the wallboard and an integral vapour barrier (walls only) ceiling sheets must breath into a vented loft, the roof covering will provide the vapour barrier. Post your reply from the shingles manufacturer for scrutiny, and we can assess the best avenue of approach…bosshogg


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## Markymark

Hi Boss

Had a short reply via email from Cembrit. He said " they wood recommend 18mm decking as a minimum."


mark


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## bosshogg

Mark...18mm OSB on a roof, better you than me. Wondered if you would care to view this www.dwbgroup.co.uk/.../Gang Nail Tr...ue. shouldn't be hard to put right...bosshogg


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## Markymark

bosshogg":2w77snr2 said:


> Mark...18mm OSB on a roof, better you than me. Wondered if you would care to view this www.dwbgroup.co.uk/.../Gang Nail Tr...rl]http://www.flickr.com/photos/markymark144/
> 
> 
> 
> 
> 
> 
> 
> Thanks for the continued help.
> 
> Mark


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## bosshogg

Mark...having reviewed the pic you posted, I agree with you. Although you are trussing your roof assembly, the ridge board (which has a live load) bears on the gable pinnacle, this load in turn is transferred via partially down these 20 degree top runners, lessening the load at the door & window slaps. In truth it would have been better to beef up these "lintels" but little harm done...bosshogg


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## Markymark

The collars are going in. I opted for the first option you specified Boss. I am using M12 Bolts as Graham specified for the connections between the collars and the rafters and I have to say they feel very sturdy.

One thing that has amazed me, I initially skew screwed the rafters down to check them in position. I found a number of the screws had sheared. This has taught me never to use screws in sheer situations as they are just too brittle!!


Upwards and onwards!!

Mark


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## bosshogg

Yeh the modern screw differs from those of old, nowadays the emphasis is on hard screws that power in through deep fluted threads, that and the tension to be found in Tanalised timber can stress the screws. One thing I always have to hand when driving in screws is a bit of soap, when the screws are rubbed on this they go in without any stress so much so I have to wind down the clutch/slip setting on my cordless, otherwise the screw goes right through, even on 60mm batons.
Once your collars are up and bolted you can push some scaffold batons onto the upper face giving you a platform to work on the roof from (through the rafters) handy for fixing those 18mm OSB boards you intend to use...good luck...the weather's certainly in your favour...bosshogg


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## Markymark

Hi Boss and all

I need to install insulation in the floor space of the home office. 

The problem is that I also want to keep insects and small mammals out of the floor space also. As the underside of the floor joists are between 6" and 3' away from a woodland floor covering I expect that it will be damp and humid. I was going to install ring beams in all the cavities and drop some OSB 3 in each cavity and then either fill with rock wool or celotex expanded insulation. My other option and a much faster one is to nail/screw 8 x 4 sheets of OSB 3 11mm to the under side of the flooring frame. I am only concerned that this may sag or rot over time. 

Speed and efficiency is my aim as I am trying to seal the whole outside office so I can safely fit the roof.

Any advice or ideas gratefully received.

Mark


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## bosshogg

Hi Mark,

Mineral wool insulation is probably best, it is neither attractive to rodents nor vapour permeable nor affected by moisture. To install, simply drape plastic netting over the joists and make pockets to receive the mineral wool. Make sure you leave sufficient space so as the wool is not squashed, but snug to the underside of the flooring, use a stapling machine to fix the netting on top of the joists. :idea: One thing worth consideration for the proximity to ground level, would be to use mineral wool slabs with a foil back, this would deter "beasties" and will reflect cold back to the ground/wind etc. make sure you cut the insulation for a close fit, don't leave any holes or you will get cold spots. The idea is to nullify any thermal transfer between inside and out, keeping all and any air leaks at bay.
You have done well to to this point so far =D> ...bosshogg


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## Markymark

Thanks Boss

I like the idea of netting. I would like some rodent proof netting or may be chicken wire would do best.

OK, I have not boarded the roof yet but I feel that as the roofing timbers have been up a while now, they wont be true and level and that when I lay the boards over them certain rafters will be a smidgin lower or higher. I am going to put a string line on to see. If that is the case what is the best course of action. I assume the collars will be the same, well I know they will be as you can see the variance. A couple of binders installed in the loft space should suffice here me thinks?


Mark


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## bosshogg

Mark...When you fit your wind boards in the loft space you might need to turn one of them on its edge, thereby giving you some extra beef to pull the collars into alignment, this is only to allow for the ease of fitting of the ceiling P/B. I doubt in the short time span we are speaking about, that Tanalised batons will have warped very much and as you are using 19mm OSB3 as your roof covering this will pull the rafters into alignment as you fully fix them. It could be worth fitting ring shank nails into your nailer so that you achieve a shake proof fix (wind can sometimes set up vibration). If you do find any rafters more than, lets say 19mm, out of alignment you can push them up using the collars (aligned and restrained by now) with suitable stub timbers wedged into place, using a hammer and nails put a restraining nail, in the collar/rafter, at the point of possible slip of these stubs. Once you have fully nailed up your roof cover boards and before putting on the shingles, knock out these stubs which will allow the roof to settle, then fix your shingles.
Assuming you have no tears in the wall outer breather/membrane you should now have a weather proof structure =D> , fit windows and door and your building should stand up to a storm if need be =P~ . If you haven't done so fit the bottom hold down straps to walls and foundation piers to finalise the structural bond to Terra Firma. All that's required now is to fit your chosen cladding, and finishings as you go :mrgreen: ...then it's on to the inside...bosshogg 8) 


> You can't help a man who doesn't tell you what he wants


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## Markymark

Thanks Boss

Great advice. Upwards and onwards, Thats assuming I can get the 8 x 4 boards on the roof in the first place.

Mark


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## Markymark

Boss


I know this is a bit after the event but. I ordered a quantity of 8'x4' OSB3 Sheets for the roof. Then someone asked me if they were T&G and I said no. This got me wondering if I should have used T&G boards assuming you can buy them at that size. Do I need to seal in any way the joints on the roof?

Also I need to install a metal drip edge at the eaves and at the rake edges. I am not sure what product I should use to create a drip edge or do Builders supplies offer a proprietary one?

Mark


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## Cegidfa

Hello Mark,
I am in the midst of finishing my roof, I used 8 x 4 x 18mm WBP ply for the roof (the minimum required by the manufacturers, by the way) All the recommendations both by the manufacturers and by my Trada Timber frame construction book say to leave a 3mm gap round each board. I used the ring shank nails as they were close. It's all about seasonal expansion and contraction. You will rarely see this adhered to anywhere, and by anyone. Knowing my luck they would have buckled and heaved and popped the shingles off, or ended up looking terrible. There is no need to seal the gaps, as the WBP and then the shingles will keep out the weather....unless you make a dog's breakfast of it...which is unlikely.
As to how to get the sheets up on the roof; if two old farts like us can do it with ease, a 'youngster' like you will have no problem :smile:
To see how, look at 'Workshop build, with a difference' in Projects, and wade through it.

As to the rake edge and drip edge; although mentioned in the shingle manufacturers website (IKO in my case) they are not available in the UK........brilliant, nowt like service. If you again, wade through my build, we came up with another way of doing the drip edge, but, we are having a fully ventilated roof...ie. continuous ridge vent as well. This is always recommended for shingle roofs as it reduces the temperature build up in the summer and prolongs the life of the shingles. I don't know if you have given any thought to this yet? The rake edge is going to have the bargeboard slightly higher than the shingles, as the wind blasts the gable end of the workshop. I may also fit a plastic angle piece over the shingles and down under the bargeboard as well. 

Have you decided what length nails to use yet? The question is, should they penetrate the roof board, or not? Again, the manufacturer recommend 30mm nails - so they expect them to pierce the board. Once again, many people disagree with this, but this is what the Americans do, and they have far more experience than any Brit. Shingles here, are for sheds, try asking a builder to shingle your house roof and watch the look on his face :shock: 

The only option that we had for the drip edge and rake would have been to buy rolls of lead, or sheets of zinc and DIY. The cost would have been astronomical, so we didn't.
I'm sure that Boss will be along to advise you soon anyway, but I thought that you might find another take on things 'interesting'.

It seemed to me, that earlier on, you were reeling under the onslaught of almost too much information, so I kept quiet, as it would have added to the angst. There is nothing worse that having too much information, when one is a little unsure. But it is nice that everyone cares enough to bother with us amateurs. It's what I love about this site - one couldn't ask for more  
If you feel the need, send me a PM, and I will do my best to help. We aren't experts, but we are both very practical minded.

Regards.....Dick.


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## Markymark

Thanks Dick

Great to know I havn't scared everyone off. This site and the proffesionals and ameuteurs who use it are what makes it. 
I was going to use cembrit felt shingles. They do talk about ventilation which I was going to do eves to eaves ventilation which I agree is not ideal as heat rises but I am unsure on the detail for eaves to ridge ventilation. That said my build is now completely covered by a large canopy of trees creating a cool spot for it. The only heat it will get is from the ambient air temperature and the wood burning stove that we will fit inside. It will however be prone to a large build up of twigs pine needles and other tree based debris.

The spec sheet for the shingles says 18mm OSB or equivelent and nails that just penetrate the other side of the boards which does seem a little dangerous for those who use there loft space. 3-3.5m ring shanked hot dip galv nails to be presise. My only concern is that the shingles can take the continous pine needle drops and dead branches. I did think of using onduline sheets but they look so commercial.


Thanks for your feedback. Greatly recieved. 

Mark


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## imageel

On the subject of nail length.. I have been building a office/workshop and decided to use cedar shingles for roof and sides and used the recommended 30mm stainless annular ring nails to affix. This resulted in piercing of the interior of the ply sheathing which in parts is showing a little moisture staining in underside of the roof (fully ventilated + cold), but slightly worrying!
Another side effect is that subsequent insulation of the walls and roofspace has been challenging as I try to push the Celotex against what effectively is a bed of nails...
Has anyone else had this problem?


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## Cegidfa

Hi Mark,
You mention the danger of protruding nails - will the roof not be insulated, or are you having a flat ceiling with insulation above? 
Ah, having re read your entry, you mentioned eve to eave ventilation, so the latter must apply. If you were to use Celotex type board between the roof joists, an airway would be created to allow for ridge ventilation. To cut costs, perhaps use thin rigid board and fill the remaining available space with mineral wool or fibreglass. For ridge venting simply cut a slot across the roof boards, to a given size. The eves gap must be larger than the roof gap, otherwise, down draughting can occur and knacker the natural flow.This link takes you to the stuff that I have bought. It comes in set box sizes, one box is £58 inc vat and del. It would be sufficient for your build. http://tapco-europe.com/ridgevents.htm

Unless you want roof storage, consider leaving it open, as a cathedral roof; that is what I have done. The feel is lovely, and in summer, will be cooler and less oppressive. I used four collar beams only, and it hasn't moved yet. People say that one is required at every stud (600mm or 400mm) but this is for Building Regs only. It will not fall down. My build is regularly subjected to gales, 30 to gusting 70mph, it is solid as a rock....so far :wink: 

Regards...Dick.


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## Markymark

Dick

I would have loved a cathedral roof but sadly I put up a traditional 20 degree roof with rafters not purlins and so I have had to put low collars in (Ceiling joists) so now I will insulate above the ceiling. 

Oh well sadly its turned in to a box, but as it will be used as a office for the Mrs I'm sure the view should suffice.

Mark


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## Cegidfa

Hello Imageel,
We are at risk of hijacking Mark's page, but, did you use a weatherproof barrier under the shingles? I found that for a while, damp appeared after the 'roof wrap' had been done. After a month of warmer weather it dried - to my relief. As to the difficulty with the Celotex, why not leave a ventilation gap, or is the insulation the thickness of the roof joists? I didn't understand the 'fully ventilated + cold' part, as you are insulating the roof?
Another build....we all need photos, to assuage the addiction  Don't be shy.
Regards...Dick.


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## imageel

Hi - yes did not intend to hijack the thread, but the nail length did mystify me :? 
The roof has breather membrane under it, but looks like there was some moisture ingress around some of the nail holes...
Rafters are 145 deep so 90mm Celotex leaves plenty of gap for ventilation from soffit up through to the ridge -which is what I meant by cold roof, it was just the walls that I had issues with as the studs were 90mm deep too..!
Regards


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## Markymark

No guys keep it up. I want to learn. I am about to shingle my roof so all this banter is great.

Mark


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## imageel

Here's my build - have since completed windows and insulation, ready for the electrics- will post some updates later



http://image-electric.com/home/albums-9


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## Markymark

imageel":3089nqg6 said:


> Here's my build - have since completed windows and insulation, ready for the electrics- will post some updates later
> 
> 
> 
> http://image-electric.com/home/albums-9




Looks great, I have to say I played with the idea of a hipped roof but decided that I was not experienced enough. 

I bet the cedar shingles were a pretty penny!!

Mark


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## imageel

The hipped roof was a bit fiddly - I used the calculator mentioned earlier in this thread http://www.blocklayer.com/Roof/RoofEng.aspx to do the calculations, and cut them either on my bandsaw or by hand. I've never done this before so it was a bit of a learning curve but worked out ok. Would have been a lot easier with a sliding mitre saw, but I was on a tight budget after paying for the shingles...
- I got them from http://www.ajsmith.uk.com/cedarshinglesframes.htm ~£1230


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## Cegidfa

Hi Imageel,

Very nice build, nice to see a hipped roof. The cedar looks rather good too. What size is the workshop...it's far too posh to be a shed :smile:
How long has the roof been finished? I still feel that it is residual damp that will dry in time..well..I hope it will!

Regards...Dick.


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## imageel

It's 4x5m but only 130ft from house line so wanted something solid and fairly well insulated to cut down noise particularly whilst planing :lol: The roof has been on since last August but as I only get to work on it at weekends progress has been slow, and with no proper workbench (B&D Workmate) making the windows particularly the cills has been challenging..
Still a bench is in progress, but need to finish th einsulation 1st


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## Markymark

imageel":1oxewy7c said:


> It's 4x5m but only 130ft from house line so wanted something solid and fairly well insulated to cut down noise particularly whilst planing :lol: The roof has been on since last August but as I only get to work on it at weekends progress has been slow, and with no proper workbench (B&D Workmate) making the windows particularly the cills has been challenging..
> Still a bench is in progress, but need to finish th einsulation 1st




Making the windows sound impressive. Sheds yes! I would love to have made the windows for my shed but I would not have a clue.


Mark


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## Cegidfa

Hi imageel,

Hmm, if the roof has been 'sealed' since last August, it should have dried out by now? Is it wise to fit the insulation yet, until the reason is found? 
You wouldn't half be peeved if you had to remove the roof lining later  
Any chance of a window construction chat, with pics of course, I for one would be very interested in the procedure. Mine are non opening, so not very challenging.

Regards...Dick.


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## imageel

I'd replaced windows on my previous house made by myself out of necessity - I couldn't afford to buy! 
I found a copy recently of the 2009 Trada doc on wooden windows which I used to design the ones for the shed - can share with you if you wish. 

It's funny isn't it what drives us to this - I have never built a shed before, what I prefer to do is finer woodwork, cabinetry etc, and I found it really difficult working with large sections of timber that were not square, that were so large they needed a home-made set square 6ft long (3x4x5 triangle) to align correctly etc etc. 
For me it was an eye opener to the different skills required, and hats of to all you construction guys who do this every day. 

For me the finished workshop will enable me to get on and refurbish a more-or-less untouched 1930's property where everything needs replacing! 
Here's an example of what I am more used to constructing in my spare time -





Cheers


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## imageel

mm not sure what happened there.. link should have been http://www.image-electric.com/home/images-103 

Dick -if you wish I'll send you the doc I worked from. Will see if I can upload some more pics of the windows later. 
The staining I was referring too happened soon after the cedar cladding went on, so I presume it was just latent moisture in the materials, it hasn't got any worse since and although I'm in part of the driest part of the country we have had significant rain since last August


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## Cegidfa

Hi Imageel,

It's good that the moisture was as thought, and has dried out. How are you managing, fitting the insulation to the Fakir's bed, AKA the roof  
Having looked at your pics of the house, you are ahead of me in 'arboreal manufacturing.' The only room here that is done, is the bathroom; that just leaves the kitchen, dining room, living room, landing/computer area, three bedrooms and oh yes, knock down the utility room and build it larger. Why do we put ourselves through this torture :wink:

I would be very grateful for a copy of the doc, thanks. 

Regards...Dick.


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## imageel

Dick,
Those house pictures were my previous residence, now wholly owned by my ex swmbo.......  my new 'old' house is another project entirely, largely untouched 1930's one complete with rubber wiring and brown bakelite light switches!

Insulation on roof slow - have about 2/3rds done over the bank holiday but even today am still somewhat fatigued! I've decided Celotex is not very nice stuff to work with - it is incredibly dusty and made worse I guess because every sheet is being cut at least 6 times - next time I build anything will stick to stud work on 600mm centers and not 400 :? 
Also the dust is quite gritty - literally every surface is covered in the stuff.. 
Actualy putting it up is not too bad, if cut reasonably accurately - am using a floorboard saw, it push fits between the rafters/studs and with a little expanding foam even the corner ones between the hip and 1st creeper are staying put!
Have mailed you re: doc
Cheers


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## Markymark

Ok

8 x 4 Sheets arrived now to get them up 10' . This should be fun!! I have made some ladder frames using 3 x 2 untreated timber. 

I will let you know how it goes if I survive. I still need to mechanically attach the roof to the walls and even though we have discussed the bat fixings before in previous posts I ordered some twist ties and some truss clips but |I cannot get a succesful fixing with either. The problem seems to be that I attached the lower chord to the rafters at the wall plate so there is three m12 bolts and two 50mm sections of timber to attach to a vertical stud running directly under the rafter. The truss clips are only 50mm wide so wont fit and the twisted ties wont attach anywhere. Any othre ideas welcome.


Mark


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## imageel

Would skew screwing the assembly either side into the top plate work? Might need to use some largish ones to penetrate far enough...
Good luck with the sheets - I managed to get mine up by myself, however your roof is somewhat higher...
Cheers


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## Cegidfa

Mark,
For my roof I used one 7.5mm Rapier screw per position, 100mm long; straight down through the roof timber into the wall plate. I know this is not the normal method, but I feel that it is stronger than two side toshed nails or screws. The Rapier screws are designed for going directly into brick walls, so they are tough. You may need longer ones for your situation: there are other manufacturers of this type of masonry screw. They may be designed for masonry, but they fix in wood a treat; I used them in the bathroom to hold studwork to the large ceiling timbers. If you are concerned about rain in the top of the fixing, apply a squirt of silicone/mastic over it, I didn't worry. Go on make your life more easy 8) 

Regards...Dick.


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## bosshogg

Mark...are you by any chance trying to fit the clips to the internal angle where the rafters, collars and wall header all inter-connect? if so try fitting them to the external where the rafter toes birds-mouth over the roof wallplates if it clear of obstructions. As you will no doubt have seen, the truss clips are very thin metal and easily bent to fit, however they look, as long as they perform. As I think I mentioned before, you also get single clips which allow you to fasten to all widths not pre-set at 50mm say.
If ness. you can also revert to thin metal joist hangers (Jiffy is one brand/name) and bend them however you choose, remember it's not the look but the performance you are interested in here as all will be covered over, either internal or external...cheers... bosshogg. 8) 


> No man is an island


 (homer)


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## Markymark

Imageel - Thanks tried this with the original rafters with 6inch hardened screws but when I came to fit the collars I had to remove them and to my amazement 90% had sheered. I do not trust hardened screws under a sheer force anymore.

Dick - Sounds intresting I will take a look at these fixings. I wanted to fasten the entire roof stucture which was calculated to have a wind load of -1.5 tons at 80mph. This is a lot of upwards thrust.


Boss. I was going to try and fit the truss clips on the outside but was a little concerned they would be too close to the elements and thet they may fail in time. I also wanted to transfer the wall plate to the studs using metal straps but I can get some rolled metal band for this.


Mark


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## bosshogg

Mark... don't worry about the clips proximity to the elements, they were designed for this, here's something to look at_ http://www.google.co.uk/search?q=roof+t ... CDwQ_AUoAQ _ 
You can see roof-wall wraps here as well which will be perfectly acceptable for your use.
Just one word on this subject - most of the time specification for truss clips - hold down straps - valley clips and all the other paraphernalia fitted to timber frame buildings, is that most, not all of course, but most often is for insurance purposes rather than for the need of the structure, how many buildings 100 years old and more are still performing perfectly with not a truss clip in sight? this applies both to traditional build and timber frame alike (timber frames were in fact the earliest properly conceived buildings, after turf or mud construction, so not as new as some would think) ...bosshogg 8) 


> You can't fix a problem using the same thinking that created it...A.E.


 (homer)


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## Markymark

OK Roof Boarded and Bitumen shingles ordered. FYI:- I managed to get a steel Drip edge as specified for these shingles. Cembrit supply one for £10 for 2.4m length. 

Here is a few progress pics. Roof was sheeted with 18mm OSB 3 Sterling board. Then covered with tyvek Housewrap.


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## Markymark

Great,

Roof is being finalised. I need some help with the windows and doors. I purchased some white upvc windows and a white upvc french door. The windows fit the openings with about 5mm gap. The question is, I need to seal them to driving rain. I was going to fit them flush to the tyvek. I need to create a sill to stop water running back in the reveal and under the window. I was going to fit a piece of lead flashing to the underside of the window opening and then down the front of the cladding (Ship lap). The problem is that their is not enough space under the window to fit lead. I will try to get some photos to illustrate what I am trying to do.


Mark


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## bosshogg

Mark...these days it's normal to affix 50 x 50 batons all round the window, the thick ness of timber is matched to the fire stopping used to. form the cavity Allow at least 50mm of the window/door frames to stick into the slap & prepare the slap as follows - line the bottom of the slap with 'Visqueen' DPM allowing a turn up at each side, this should stop in the cavity between your timber frame walls and final cladding. It's important to bear in mind that the membrane (in your case Tyveck) is a secondary water proof skin should the outer cladding fail, similarly any cill flashing should be treated the same _i.e._ a secondary drip. The cavity created should be positively vented thereby allowing any secondary drips to dissipate, the real waterproofing should both be, and maintained, to the outer cladding. Hopes this helps...bosshogg


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## Cegidfa

Hi Mark,
Boss and I must have entered our entries together, his wasn't there when I started....Hi Boss - two minds with the same thought :smile:
For my cill pan I used Sika MultiSeal-S flashing tape. The water (should there be any) will run down behind the cladding and out at the bottom - which should be open, apart from insect mesh.
The wind and warmth will dry it out; this way you don't get water marks on the cladding face.
This is the American way, and they have far more experience of timber frame than we do.
Don't forget that the inside part of the cill pan needs to be turned up, or, just lifted a bit to create a slope. See below how mine is done, apart from lifting the back, which will be finished with the inside. 





Hope that is of use....Dick.


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## Markymark

Nice job Dick. I was wondering how to flash over the ship clap cladding also? 

P.S. The vented ridge went on a treat. 

Some photos here...




















Or for all images visit :-http://www.flickr.com/photos/markymark144/

Thanks Mark


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## Cegidfa

Hi Mark,

Glad the roof vent went ok. You have now caught me up as my vent is finished also :smile:
The shingles look good too. How did you overcome the fact that the shingle isn't wide enough
to cover the vent in one go?

Regards....Dick.

Just answered my own question by looking properly at the photo. You bought three tab shingles :roll:


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## bosshogg

Mark...I'm perplexed, the middle pic in your last post (floor construct) you appear to have in filled in between the joists with cuts of OSB, just interested why?...bosshogg


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## Markymark

Dick - The Cembrit 3 Tab Felt shingle seemed to fit just fine. They overhang the sides of the vent just slightly (10mm ish).

Boss - I paneled in between the floor joists so that I could keep the animals at bay and also to use to support the rockwool. I was going to panel the underside with full sheets but went for the more involved individual sections as I thought if any began to fail I would be able to repair individual sections. Do you think it will work?


Mark


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## bosshogg

Oh that was why, just make sure they can't fall through when joist shrinkage takes place and allow for expansion. netting and solid bat insulation would achieved the same rodent prevention, and cost less to boot, but otherwise spot on mate...bosshogg  


> You can't help a man who doesn't tell you what he wants :|


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## Markymark

Thanks Boss

The boards are sat on 19mm batons. Most have a 3/5 mm gap leaving 14mm to sit on all round.

The OSB is OSB 3 so even though it is not in direct contact with moisture it will get damp some days. I just hope the OSB 3 does not rot and fall out too quickly. I am over boarding with 22mm TGV P5 V31? Moisture resistant chipboard. I assume this stuff once laid wont be easy to take up so any work can be undertaken underneath from a individual panel.

Next stage is to fit the floor and then first fix electrics which I am undertaking myself then getting certified by a sparky. 

I am cladding the imperial stud centres with OSB 9mm and then I am over boarding with 8x4 Bead & Butt MDF Panels to give it that boarded out feel. Not sure how to finish the roof yet. 


Its great to have a watchful eye. This forum is absolutely great for us Hobbyists.

Mark


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## Markymark

Hi

I need to prepare to clad the outside of this building. I am using redwood ship lap timber that is VAC VAC Treated. Not sure what VAC VAC is the only reference is that the product used may be a arch timber preservatives product, but I am not sure? Can anyone spread any light on this treatment and what finishing stain I should use with it. Water/Alcohol based? 

I need the name of a good brand of finishing stain that I can apply to this and will have maximum time before I have to reapply. Ideally I would like to apply this using a Spray gun for speed and uniform finish.

Any help gratefully received.

Mark


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## Cegidfa

Hi Mark,

Try this link for an explanation of VAC VAC. 

http://www.wenbans.com/services-treatment.php

As to finish, we are going with Cuprinol Garden shades, as we have used that at our old house - on the fencing and bridge. 
It lasted well, so we will try it again. It can be sprayed. Don't forget, paint *all surfaces* once, then fit it and paint again.
This way it will last longer - if more expensive. Coating all round reduces the chances of the bare back absorbing water/vapour and causing 
cupping and splitting with seasonal shift. I got this from watching Tom Silva on This old House...err...many years ago.

Regards....Dick.


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## Markymark

Thanks Dick. I think I am on the right track.


Mark


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## Markymark

Hi

I have a problem. I have got to the point where I am fitting 2.5mm Twin & Earth Cable for the ring main. I Have fitted it straight down the middle well away from the studs just in case it gets hit by any fixings. I am reading all over that it is a risk to install electrical wiring within thermal insulation and I would agree. The build has enough combustible surfaces including being under a canopy of Pine trees 60 ft high to cause a lot of problems if it went up in flames. I read there is a BRE publication that explains all I need to know out working with thermal insulation and electrics but it is £39.00. Why oh why do they charge for safety information???? 

Can anyone help me as I have filled in between all the other studs with 90mm Xtratherm and I am about to install insulation between the studs with the cables running through?


Thanks Mark


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## Cegidfa

Hi Mark,
Have a read of the info below for the latest view. 
If the wiring is in a wall, the heat 'duty' is less onerous than in the roof, which will have a greater amount of insulation.
As the guide says, you could use a higher temp. rated cable, or, up the size a notch, as stated.

Regards...Dick.

http://WWW.electrical.theiet.org/wiring-matters/15/current-ratings.cfm?type=pdf


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## imageel

Mark - I think there are derating tables in the IEE 17th edition reference thingy I have - will have a look and post what the formula is. Are you sure that you are putting the cable runs in acceptable places? - there are regs for the zones where they are permitted to run (roughly in line vertically or horizontally from your sockets/switches.
One question though - why are you insulating this void - surely 90mm insulation in your neck of the woods is sufficient, and putting another layer may cause condensation problems since your cable exits to your sockets will pierce your vapour barrier -won't it?


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## Markymark

imageel- 

Thanks for the reply. I have a electrician come round as he is certifying it under Part P. He wanted to see the wires in the structure before the insulation or plasterboard. He has looked and said he is happy. I should have asked the question with him before he disappeared. He is coming back to install the armour cable between the garage and the shed, I am trying to get things moving so feel a little impatient.

With regards to the insulation. This is the only insulation in the wall. The studs are 90 x 42 PAR ans so it made sense to fill in between the studs with solid insulation. I agree with the sockets effecting the vapour barrier but I am not sure how I would get round this? I can only assume putting expensive plastic surface trunking around the walls but that would look unsightly and would be expensive.

Dick - Thanks for the info I will take a look. I have standard 2.5mm T&E cable installed and some people say that the expanded foam can react with the PVC sheathing on the Cable. Also any heat created by current flow will only collect in the cable and possibly overheat? Does 200mm of rockwool have a higher value than 90mm Celotex or equivalent foil backed expanded foam insulation?


I'll look forward to your post.

Mark


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## imageel

Mark,
Perhaps I have misunderstood - so from the outside wall inwards you have -
cladding, permeable membrane, studding (infilled with insulation), vapour barrier,small void for cabling, whatever material to finish presumably ply/plasterboard.
I thought you were thinking of filling your service void i.e. around the cables, with insulation, apologies if I was mistaken!


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## Cegidfa

Hi Mark,
The answer is that 200mm of rockwool is .21w/mk and 90mm of PIR is .24w/mk (approx). So the rockwool wins.
I too have read of the reaction between foam and cable. If you have some 50mm tape left why not cover the cables in it.
Or, staple some polythene/plastic over the cables, as an interface, and then add the foam?
As to heat 'collecting' in the cable, the cables are presumably clipped to the studding? Don't lose sight of the fact that wood is a 'thermal bridge'
these days. and the insulation is on one side only  And you won't be running high current machinery all day/every day...will you :shock: 

I have had the loft cables under 500mm....yes, 500mm of rockwool for some time now, and the loft is as hot as Hades...naff all ventilation of any worth.
I have monitered the effect, i.e. discolouring/ stiffening,etc and found none to date. Yes, if you seriously overload/overheat cable consistently, you are asking for trouble,
but in a domestic situation such as yours, you are unlikely to have a problem. I had an unconventional approach to what was and wasn't 'safe' at work.
It's all about undestanding your environment, and using that knowledge wisely, not following 'rules' blindly.

Regards...Dick.
PS. With regard to piercing the vapour barrier when fitting the sockets.....don't worry, unless you are going to have a bath in there :shock: 
It is not a house....I'm the anal one here, and I won't be fitting a vapour barrier, it's a waste of money.


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## StarGazer

The reaction between insulation and the PVC buffer on mains cable is for expanded polystyrene (white crumbly stuff) which leaches the plasticiser out from the grey/white outer insulation on mains cable. 

Mains cables are not affected in the same way by PIR foam (celotex etc) insulation boards.

If the cables are buried in the insulation in the walls then they should be derated as another poster has already stated.


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## Markymark

imageel":4isprefs said:


> Mark,
> Perhaps I have misunderstood - so from the outside wall inwards you have -
> cladding, permeable membrane, studding (infilled with insulation), vapour barrier,small void for cabling, whatever material to finish presumably ply/plasterboard.
> I thought you were thinking of filling your service void i.e. around the cables, with insulation, apologies if I was mistaken!



imageel - From the outside in Shiplap, 11mm OSB 3, Studs, Rigid insulation in between Studs, Vapour Barrier, OSB, 9mm Bead & Butt Board.

The mains cables run down the between the Studs. Not attached to the studs. through to a metal plate supporting the steel back boxes. 

I will get a photo on soon. 

To fit the Insulation I would have to cut a piece in half and trap the two cables in between it like a sandwich. Alternately I can cut a channel out of the insulation for the cables to sit in and loosed some of the value of the insulation.

Hope that is a little clearer? It should be clear on the photo appearing.

Thanks all

Mark


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## Markymark

Thanks Star Gazer

That seems plausible. I think the total current capacity to the office is derated as the feed to the garage is too small so the sparky is puting the garden office on a 16amp MCB.

Mark


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## Markymark

This is a photo of the corner with the wiring running down the centre between the studs.


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## Markymark

Thanks everyone so far.
Everyone's help has got me this far.


I have finished the insulation and vapour barrier which I Took behind the socket backs. I am cladding the walls, due to the fact that my studs are at 2ft centres to allow easy fitting of 8 x 4 sheeting on the outside, internally with yet more 11mm OSB. Then to avoid the plasterer, I will install 9mm butt & Bead MDF panels. This should give it a T& G appearance. I was going to install the OSB on the ceiling also but wondered if I could have some ideas from anyone on how to finish the ceiling off. Don't fancy the Bead & Butt panels on the roof also so not sure how to finish the ceiling???


Any ideas?

Mark


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## bosshogg

Mark why not fit plasterboard , OK at 2' centres you'll have a bit of cutting, mind you only 1:1/2" or so if you use the 2.4 x 1.2 boards. You'll need two to fix these to the ceiling joists/collars, and dwangs/noggins will have to be fitted in straight lines at 1.2 centres, it's something of a learned technique, but the result is a normal looking ceiling...bosshogg  


> Ethical axioms are found and tested not very differently from the axioms of science. Truth is what stands the test of experience. *A.E.* (hammer)


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## Markymark

Thanks Boss

Good Idea, but I am trying to keep trades down to a minimum due to costs escalating. I was going to try a panelled ceiling. I was going to arrange the boards symmetrically and use a small timber trim to cover the joint and so give it a panelled look. What do you think?

Mark


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## bosshogg

Sticking with plasterboard, which in my opinion is the way to go, you can buy small sheets which a single pair of hands can install and to assist you can make up a pair of soldiers ('T' topped sticks) which you position as you progress, pull under the sheets, to jamb them in place whilst you screw them up. I could talk you through hand taping the joints if you want, or you can use square edge boards covering the joints with thin straps too form a Jacobean type of ceiling. Every bit as easy as what you are already considering...bosshogg  


> I never teach my pupils. I only attempt to provide the conditions in which they can learn. *A.E.* (hammer)


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## belcher

i come at things from a fencing background so my approach may be way off but all i did was concrete six large posts(5x4)3m long in the ground about 800mm then build your shed off of those,no need to dig out soil to level the ground,bolt on your floor supports, bolt on your roof using a single slope roof,sometimes called a pent shed design. Nail your shiplap to the outside,nail your ply to the inside,cut off what you dont want from the top of the posts.


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## MickCheese

For the ceiling I would go with plasterboard. 8X4 sheets are not a one man job but with some made supports you can do it with two. Then just tape and plaster the joints, a heavy lining paper will give a good surface to paint.

Just need a friend for a day to help.

Good luck.

Mick


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## Dibs-h

MickCheese":2h51sbn4 said:


> 8X4 sheets are not a one man job



I can testify to that! :mrgreen: 

Dibs


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## No skills

Dibs-h":13qqqzkb said:


> MickCheese":13qqqzkb said:
> 
> 
> 
> 8X4 sheets are not a one man job
> 
> 
> 
> 
> I can testify to that! :mrgreen:
> 
> Dibs
Click to expand...



I wish somebody would convince my boss of that, who thinks we should be able to fit 8x4 12mm ply up to celings single handed (and quickly!) :lol:


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## bosshogg

No skills":1x7b9mus said:


> Dibs-h":1x7b9mus said:
> 
> 
> 
> 
> 
> MickCheese":1x7b9mus said:
> 
> 
> 
> 8X4 sheets are not a one man job
> 
> 
> 
> 
> I can testify to that! :mrgreen:
> 
> Dibs
> 
> Click to expand...
> 
> 
> 
> I wish somebody would convince my boss of that, who thinks we should be able to fit 8x4 12mm ply up to celings single handed (and quickly!) :lol:
Click to expand...



H&S say no and it's your right to contact them to have this practice stopped. That applies to anyone working in the construction industry, a risk assessment would identify this and show another method would *HAVE* to be found...bosshogg  

Just as a foot note, anyone knowingly performing illegal duties is doing so against the law (Regs in a court of law - are laws) (hammer)


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## Cegidfa

Well said Boss,
The number of times that I was _told_ to bypass a door safety switch...or else, by managers and Team Leaders, are inumerable.
Funny how the threat vanished when they were asked to 'put it in writing" on official company paper.
And this on lethal equipment, such as a massive filling machine canning at 1500 cans per minute.

Regards...Dick.


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## Markymark

Hi

We are only slow at the moment. Walls are covered and need to fit the ceiling. I need some advice on how to connect the struts to the rafters to strengthen up the roof. I was told to use Ply glued and screwed to either side of the connection. I have 28 of these connection to do and wondered if I could use my nail gun and nail them instead? Would it be strong enough? 

Advice gratefully received.

Thanks

Mark


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## bosshogg

Hi Mark...The conventional way is way is to glue and screw the plywood gussets to both rafters and collars, but assuming you use ring shank nails in the nailer it should be ok. Screws are used to impart a compressive force, effectively pulling together both surfaces, reducing the shrinkage/expansion at these areas and thereby reducing the chance of de-lamination. When you think about it, ring shank nails will provide a similar force, and it won't be the end of the world if you had to repair some in the future, just a pain...bosshogg  

Some Scots colloquial -


> Errapolis :The constabulary is approaching.Usually followed by "Ah'm gettin the f*@k ootae here"


 :lol: :lol: :lol:


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## Markymark

Thanks Boss

Upwards and onwards.....


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## Markymark

Hi All

Its been a while. I have cladded all the interior with 8 x 4 Bead & butt sheets giving the interior a instant TGV panel feel. I am very pleased with this. I have now come to the finish joinery, Architrives, skirting reveals. 

As my UPVC windows are smooth with the outside wall this has created a reveal which I need to frame out and attach achitrive to. 

I have no idea how I should do this as the UPVC windows are fastened to the studs using plastic screw on tabs that project internally. I will post some photos soon as I need to explain myself. Can anyone advise me on framing out the reveal and fitting the achitrive. Measuring and cutting.


Mark


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## bosshogg

Post photos first and let us have a look...bosshogg


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## Markymark

This is the window frame showing the plastic window retainer.

I need to box these out and fit architrive. 

I need to buy some stock now as the decorator (father in law) is here!!

Mark


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## bosshogg

Couple of ways you can do this. 
First a favourite way of the replacement window boys, build up plastic packers off the framing, with silicone cementing the packers together 


making sure that they are both perpendicular to the window frame, aligned and straight to each other (don't expect symmetry to any of the framing except the window frames) Set the cill in place (normally 30 - 40mm proud of the wall) cut and stitch an apron piece in place and with the top plate cut to a snug fit, so as to hold it in place, measure the distances between these at the side plate placements, (these should be the same, 1 - 2 mm doesn't make a whole lot of difference, any more go back a step or two) once cut square and assembled you should have the windows framed with ingoes (window plates) witch are open on the face i.e. you can see the fixing brackets, packers etc. This void should be filled with expanding foam, enough to allow a small protrusion into the room when it's set, using the fixed plasterboard as a guide, cut the set excess foam flush between it and the edges of the ingoes, this will both glue, seal and insulate this troublesome detail. Cut and fix your facings (architraves) and replace and nail the apron piece, removed to allow for foaming.
Expanding foam produces quite a lateral force when it is pumped into a trapped space, so make sure you have some pressure sticks handy to shore as required.

The other way to do it is simply to cut and fit timber packers, scribing over fixing plates etc. still ensuring perpendicularity and straightness, nail these around the window. Either pack the voids out with glass wool insulation so that when the ingoes go on all is snug, or as above, or a mixture of both. Nail and fill as required your facings, then paint to suit.

The first procedure is especially good if you want a varnish finished trim around your window, as it has limited nail heads to show, both should show similar to this



Cheers...bosshogg


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## Markymark

Great Help Boss.

Not sure on the terminology $&*^%$%^. 

Do you have a close up of the window casing without the achitrive. What I have found is that the window openings are not exactly square so I will need to square the casing ( not sure of term) so it is square.

Thanks


Mark


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## Dibs-h

Markymark":34zgt8r1 said:


> Great Help Boss.
> 
> Not sure on the terminology $&*^%$%^.
> 
> Do you have a close up of the window casing without the achitrive. What I have found is that the window openings are not exactly square so I will need to square the casing ( not sure of term) so it is square.
> 
> Thanks
> 
> 
> Mark



If the windows openings aren't square to the windows - just insert whatever is require or to hand to square the reveals. Be they plasterboard or timber reveals. You could use strips of timber to space off the reveals\sill or foam it and use some form of temporary fixing.

Mine weren't absolutely square and I used both methods.

Dibs


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## Markymark

Ok 

I am cladding the walls now. The inside has finished we are using the great new space. Thanks for all the advice from everyone. 

I need to flash above the windows and doors so if any water gets under the shiplap it does not go into the window heads. I have a roll of Code 4 Lead which I am going to use but wondered if anyone had any advice for me on how to flash correctly. 

I was going to cut a slit in the tyvek above the window and push up a piece of lead slightly wider than the window and then attach it with a timber batton? The lead skirt would then be moulded in to a small drip edge just above the window frame.

Update - I am up to the top of the window frames with the shiplap and I have a difference in height in the shiplap. All four shiplap piers have ended at a different point at the top of each window +/-1" Does redwood Shiplap have a tolerance? I need some help on how to make right.


Thanks Mark


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## Markymark

Ok. All done. I used Code 4 ead flashing above windows and doors. Took a bit of work but I think it will work very well. I am really pleased with the overall finish. My only gripe is that the recommended fastening for 4" redwood shiplap was with a single nail on each strip. I would have loved to had them secret nailed but to stop the board cupping it needed to be this way. 

Any how I have the other three elevations to shiplap and then to Tongue and Groove the soffits and install ventilation holes. Then Fasias and Bargeboards and Hey presto the finished article. I will post some photos soon.

Mark


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## Markymark

The finished shed... woops Office!! Thanks Everyone who helped


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