# Workshop\Shed Construction



## wizer

Well after nearly a year i'm back to planning a workshop. It's been a bit of a nightmare what with kitchen plans, garages and useless builders, etc etc (I won't bore you with the details). 

So following on from this old thread, i've now made a firm decision to build it out of wood and do it myself.

Briefly, it is a wooden lean-to building with roller doors at the front and double doors at back. External dims roughly 4.6m x 2.4m 

I'm currently designing the roof and wondered if I am on the right tracks:















Is this the right sort of joint for the rafters?


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## Jake

The simplest way to attach the rafters to the house wall would be to rawlbolt a beam along it, and hang the rafters off that with joist hangers - saves all that other timber you have against that wall (and space).


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## Freetochat

Jake":11atgcv4 said:


> The simplest way to attach the rafters to the house wall would be to rawlbolt a beam along it, and hang the rafters off that with joist hangers - saves all that other timber you have against that wall (and space).



Unless you are going to insulate and line with boards rather than a brick face?


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## Jake

Freetochat":2zn28fs4 said:


> Unless you are going to insulate and line with boards rather than a brick face?



Why would you insulate what is becoming an internal wall?


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## wizer

yeh cheers, it will be insulated and ply lined, so for aesthetics it will be best to have the extra frame work.


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## wizer

Jake":17kpsnef said:


> Freetochat":17kpsnef said:
> 
> 
> 
> Unless you are going to insulate and line with boards rather than a brick face?
> 
> 
> 
> 
> Why would you insulate what is becoming an internal wall?
Click to expand...


sound insulation more than anything


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## Shady

Wizer, having read the 'old' thread, 2 observations:

1) Agree with the point about needing to access the gap between fence and shed for maintenance: who 'owns' the fence, and how 'friendly' is the neighbour: I say this because the best way of solving this and maximising every inch of space would be to replace that section of fence with the workshop's 'outer side'. You could make it look almost unchanged with careful design, I suspect. Offer to re-proof the whole fence once a year in return??

2) Light: I'd make the entire roof out of the 'see-through wriggly perspex' stuff. It makes a tremendous difference, and is a cheap way of doing one. I've just used some to make a quick lean to for bicycle storage. With proper rafter spacing, it's quite strong and permanent enough. Good luck!


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## Jake

In which case, you'd be better hanging the rafters off the wall, and stepping the internal wall off the house wall by a cm or two leaving a gap between the two - decoupling is the most effective form of reducing vibration/sound.


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## wizer

Shady:

1) I have considered this... what about the gutter overhang? I think to save any complications i'd rather keep the fence in place. The fence panels slide out easy enough so re-treating wont be much of a problem. I need to consider how to finish the 'unseen' side. Felt?

2) Light is somehting I do need to think about. My father suggested the same stuff. Will it be prone to leaking? How would you fix it to the rafters?

Jake, cheers I will look into that idea.


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## Shady

It's very waterproof - impervious, in fact. IIRC, you allow a 2 'wriggle' overlap where sheets join - could always run a bead of clear silicone in for absolute assurance, I guess. 

Fixes with special screws/plastic washers/spacers, sold in packs wherever you get the materials from. (Travis Perkins seem reasonable) Also available are shaped 'end pieces' that fill the gaps so that it's draft-proof. If light's an issue, I'd take a long hard look at this stuff: it's easy to work with, very quick to install, lightweight, and will maximise your light. I think it's also got a 10 year guarantee, from memory... I'll try and find the website - lost it just now...

OK - found some stuff: Flashing advice here:

http://www.cavitytrays.co.uk/pdf/damp_proofing/Type F.pdf

General advice here (a good link for an overview, with details on overlaps, fixing etc):

http://www.diydata.com/projects/cor_roof/cor_roofing.htm

Initial costing info here:

http://www.casupply.co.uk/acatalog/pvc_roof_sheets.html

From the same site, accessories, fixings etc:

http://www.casupply.co.uk/acatalog/corrugated_fixings.html


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## wizer

Blimey, thanks so much Shady, something for me to read up on. I like the idea alot.


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## Shady

No Probs: the only downsides that I'm aware of are 

a) it's not very aesthetically pleasing... (!)

b) thermal properties: check on UV absorption/siting of your shed with respect to the sun: you might broil yourself in summer - although if it's that hot, nice to work with the doors open - and it won't offer a lot of insulation in the winter - but a shed that size should be nicely heatable with some sort of thermostatically controlled wall heater, I'd think...


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## Jake

A more expensive, but more aesthetically pleasing (and better insulated) option would be to use twin-wall poly like a plastic conservatory - look in Screwfix for example - twin wall stuff

.


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## wizer

Looks good too Jake. I'll have to look into how to install it. Do they have a flashing solution as per the corrugated stuff?


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## SketchUp Guru

I'm wondering how you'll close the join between the wall and roof next to the brick wall. Have you given that and thought?

I think I would change the rafter joint up at the top of the high wall. As it is now, it looks like a split waiting to happen. Perhaps a ledge or blocking (like a bracket) run underneath each rafter would take care of that.

I like the "wriggly perspex" idea for letting light into the shop. Here in the US it's fiberglass. there is a wooden strip available that is milled to fit the corrugations. If that is available, suppose you put two pieces back to back on top of a layer of the W.P. and another layer of W.P. on top of that. It would give you an airspace to act as an insulator

You could also make some isulated shades to open or close to control how much light you get in and how much heat comes in or out.


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## Shady

> I'm wondering how you'll close the join between the wall and roof next to the brick wall. Have you given that and thought?



Over here it's called 'flashing' Dave: for traditional roofs meeting brick (which the majority of our houses are) you cut a channel into the mortar between two courses of bricks at the appropriate height, and press/hammer in the top edge of lead sheeting, which then lays down onto the roof. It's then mortared into place. For these sort of things, there are plastic alternatives: I suspect they'll need some sort of silicone gunk along the top edge - haven't used them myself...


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## SketchUp Guru

Thanks Shady for the explanantion. Actually I wasn't thinking about that join but rather between the shed wall and roof. 

The flashing does make sense to keep water from runnning down in between.


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## wizer

grr after spending a day on more shed design, sketchup decided to not save when it said it had! :evil: I've tried to recover the changes, but no luck.... back to square 1 (or rather square 3 or 4)

Partly my fault I suppose as I was running it on Windows Vista Beta 2

I'm not really sure where the problem lies in that joint Dave? Where is the weakness?


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## SketchUp Guru

I could be wrong but it seems to me as if that notch would be a great place for a stress riser--a place where a crack could easily start--if there is much of a load on the rafter. Of course I'm thinking of snow loads such as we commonly get here in Minnesota in the winter (and once in awhile in the summer. )


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## wizer

ah ok cheers Dave I see it now. Not sure wether this is a problem or not. We do get snow but not often and not often that heavy. I suppose the solution is to just sit the whole rafter on top of the frame work


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## DaveL

WiZeR, 

That is a weak point but cutting the notch so you remove a minimum amount of timber should be ok, I think you picture shows a deeper cut than is needed or use a metal hanger so the load is on the bottom edge of the rafter.


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## mahking51

Wizer
Just finishing off a similar shed but not a lean to type.
Important thing IMHO is to go for a fibreglass flat roof, spend a little more at the start then forget it for 20+ years!
Mine is 1/2" shuttering ply trimmed flush all round then covered with bonder then a layer of 600gsm chopped strand mat and finally a heavy topcoat of waxed gelcot. Edges are prefromed GRP roofing channel; front is preformed GRP dip channel and rear is drip channel into guttering. Comes in any colour (olive green) and will look great.
Over the years I have totally had it with roofing felt and corugated materials.
Will post some pics beforethe roof goes on.
Regards
Martin


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## mahking51

Here are some pics of the shed; roof goes on tomorrow!

















Here are two details of rafter setup, note small wedges to avoid having to cut rafters; there will be a fillet of 1/4" marine ply between rafters to bring up to level for roof boards.









Interior is filled with 25mm poly insulation covered by shuttering ply; windows are to be opaque security glass with wire inside.

Regards
Martin


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## wizer

ooo lots of questions Martin!

Shiplap on the outside?

What is the black material between the wall and shuttering ply? 

Are you running electric into the shed? If so how do you get the wires around the poly insulation?

what are the dims? Mainly the height front and back?

What are the dims of the timber? 2x4? or 2x6?

Was there any reason you used planed timber?

I'm not sure I really understand what your doing with the rafters? What are the dims of the fillet pieces and why did you not use timber of the same dims as the rafters?

I also note that you have the rafters laying flat as apposed to on their side. For some reason I hadnt considered this, I guess this makes sense and will add strength to the roof.

I'd like to see a picture of the finished roof as it's hard tp picture from you explanation. "_bonder then a layer of 600gsm chopped strand mat and finally a heavy topcoat of waxed gelcot_" not sure what any of that is lol 

The main reason i'm considering the twinwall roof is for light. There will be only one window at the back end of the shed in the door. The other alternative is to put in a couple of 'Bubbles' or Roof Windows.

Thanks for posting your pics, it helps to see something like this in progress.


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## dedee

Wizer,
Have you considered corrugated bitumen roofing sheets, Onduline ? http://www.slecladding.co.uk/ondul.htm

I've seen it used extensively in France and have used the lighter Corroline on a shed here. Opening rooflight windows are available and although this is not from experience I reckon this would last longer than the plastic variants that must become brittle and discolour over time. 

It is certainly very easy and clean to install.

Corroline is available from Wickes, Homebase etc but I guess the windows would have to be ordered.

Andy


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## wizer

that's it Andy, go and throw another one in there to confuse things! 

Looks good actually, i'll have to see how pricey it is


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## mahking51

Wizer,
Shiplap outside is 16x125mm treated, 67p +VAT per m from Blamphayne Timber in Devon, 9.5m run per square meter of area.

Black Material is standard semi permeable roofing membranwe stapled over the studding; shiplap goes over this on the outside; layer of 25mm poly on inside then inner lining of shuttering ply.

No electrics in shed, it is going to be just for storage with timber racks and old kitchen cupboards to keep all the stored rubbish out of my workshop!

Shed is 19 feet long by 6.5 feet wide; 6 foot 6" at front; 6 foot at back.

Framing timbers are nominal 4x2 (89x38mm) CLS treated timber for base mounting and nominal 3x2 (63x38mm) CLS for studding; 4x2 CLS for rafters. CLS is cheaper than normal sawn 4x2; 3x2 etc and much nicer to work with. I allowed about 5% over for warpage etc which was about right.

The 1/4" fillet pieces are only for the front edge to take up the slope (5 deg) of the roof rafters so that the ply boards sit flat. They are just strips of scrap ply.

4x2 rafters are falt to give more fixing width to roof boards and also to keep overall height down.

Have now got windows in and roof on and glassed but have to wait until Monday early morning to put on top flowcoat as it was way too hot to apply after the glassing, would never have cured properly.

Have had to abandon safety glass as it was £42 a pane, silly money so have gone for ordinary float and will spray opaque on inside.

Will post some more pics later.

Regards
Martin


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## wizer

thanks for the info Martin, has helped with my plans a lot.


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## wizer

right, i'm moving on with my design now. I have slightly adjusted that rafter joint to make it more meaty. 

I'm putting the roof detail on the back burner for a bit while I research all the options.

The front is going to have a rolling garage door. I need to find some technical drawings on these to find out how I design the front end of the shed.

On the back of the shed I want double doors across the full width. To maximise on light I want them to have large glass panels in. Could anyone suggest a method of constructing the doors? I have mocked up just a frame to illustrate where the doors are going. Can the doors be made in much the same way as the wall frames? I'm thinking about cladding the back of the shed with something nice like Cedar or Oak, so would like to build this into the design of the doors.






Current Sketchup File


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## mahking51

Wizer,
My first thought is that if you are having a roll up door the top lintel needs to be quite substantial, more than just a 4x2.
Also I believe that you need some head space above the lintel for the door to roll into which is lacking with a lean-to design because of the slope of the roof in the end frame.

I have added two or three small vertical noggins between the horizontal lintel and the sloping rafter for strength.

Regards
Martin


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## wizer

thanks martin, I had considered the headspace problem and then just decided to ignore it in the hope that it'd go away! :roll: I need to find a product and then find out measurements. I guess a little over hang wouldn't be too much of a problem. hmmm maybe an up-and-over door, but personally i hate them.

I had also considered the noggins between the horizontal lintel and the sloping rafter, but I was too lazy to draw them!


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## mahking51

Wizer,
You might consider having two conventional doors but with one of them working in 'fixed' mode whereby for most of the time it is locked shut forming an end return wall with the 'real, normal' door closing to it.
Then if occasion demands, it can be easily opened wide for better access.
I would have done this but was restrictd for total width.
Regards
martin


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## wizer

ahh if only Martin. The front of the shed slopes up quite steeply. So the doors would have to open in. Not ideal. 

But I like your idea for the back doors and am going to adjust it so one door is smaller than the other.


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## wizer

Hi guys, we're getting close to the start of construction now! I'm like a kid waiting for xmas!

I need to think about cladding. One wall is going to be fixed to the house, the other will be just 15cms away from the fence and so will not be seen. How do you think I should finish this wall? Just board and felt? or shall I use weather board?









Also the front and back will need cladding. As this is the front of the house and the back looks onto the garden AND its a relatively small area, I was thinking of cladding it with something 'nice'. But not sure what? Shiplap? Hardwood? Something else?

Would appreciate your views.


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## WellsWood

So you're going indoors finally then? :wink: Like your design Wizer, I wish I could find the time to learn SU. Hmm...think of all those "winter" projects you'll be able to do.

OK, I might as well stick my twopennyworth in. A few thoughts in no particular order:

1. I would definitely bolt the wall plate to the side of the house and use joist hangers. I have used this method a few times now on similar projects and they're all still standing. It will add considerably to the stability to have the whole thing attached firmly to the house.

2. If you're going to use any kind of corrugated clear roofing you need to be aware that it will be very noisy when it rains. It also has very poor thermal properties: it stands a good chance of being a greenhouse in summer, and a fridge in winter.

3. I agree with Martin, Roller doors are heavy and I'm not convinced your structure is up to the job. He's also right about the fairly large space over the door to roll up into - have you got the headroom? What about one of those segmented up'n'over GRP things? - might be more suitable (and probably a lot cheaper).

4. You will need to make sure that the _entire_ stucture, including any guttering, is on your side of the boundary. Otherwise it is feasable, no matter what your current neighbour says, that should the house next door change hands the new owners could make you remove the offending bits. A hassle best avoided at the outset, I believe.

5. Have you thought about security? If you're going to fill it with tools, and considering it appears to be visible from the road, you might want to be very careful about working with the door open on that side. It only takes one wrong'un to wander by and see in for you to get a late night visit. With this in mind my thoughts would be that a more substantial roof made of ply would be more suitable. You could always fit rooflights and if they were the opening kind you'd get some ventilation back to make up for having the door closed. It makes little sense (to me) security wise to fit nice strong doors and locks to something with a roof that can be opened with a penknife.

Good luck with your build anyway, give me a shout if you need a hand, I'm only down the road.

Mark

p.s. Martin, I hate to be a wet blanket, but I think you'll live to regret putting your rafters "flat". Even a relatively short length of 4x2 will sag over time just under it's own weight when laid like that, and from your pics it looks like CLS - about 38mm thick? - unlikely to take your weight while you're up there putting the roof on. Falling even a few feet onto concrete can hurt - a lot!


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## wizer

MarkW":evcke2y7 said:


> So you're going indoors finally then? :wink: Like your design Wizer, I wish I could find the time to learn SU. Hmm...think of all those "winter" projects you'll be able to do.



thanks for your comments Mark. It will be great to come in from the cold. 



> 1. I would definitely bolt the wall plate to the side of the house and use joist hangers. I have used this method a few times now on similar projects and they're all still standing. It will add considerably to the stability to have the whole thing attached firmly to the house.



Cheers, the wall will be bolted to the house



> 2. If you're going to use any kind of corrugated clear roofing you need to be aware that it will be very noisy when it rains. It also has very poor thermal properties: it stands a good chance of being a greenhouse in summer, and a fridge in winter.



Should have updated this thread on that. I have infact decided to go with a solid sheet roof with maybe some rooflights or a dome. The main reason for this was the cost.



> 3. I agree with Martin, Roller doors are heavy and I'm not convinced your structure is up to the job. He's also right about the fairly large space over the door to roll up into - have you got the headroom? What about one of those segmented up'n'over GRP things? - might be more suitable (and probably a lot cheaper).



I have spoke to the manufacturers of the rolling door and they seem to think it will be ok. The design incorporates the right amount of headroom for this.



> 4. You will need to make sure that the _entire_ stucture, including any guttering, is on your side of the boundary. Otherwise it is feasable, no matter what your current neighbour says, that should the house next door change hands the new owners could make you remove the offending bits. A hassle best avoided at the outset, I believe.



Yep, the whole thing is within my boundaries.



> 5. Have you thought about security? If you're going to fill it with tools, and considering it appears to be visible from the road, you might want to be very careful about working with the door open on that side. It only takes one wrong'un to wander by and see in for you to get a late night visit. With this in mind my thoughts would be that a more substantial roof made of ply would be more suitable. You could always fit rooflights and if they were the opening kind you'd get some ventilation back to make up for having the door closed. It makes little sense (to me) security wise to fit nice strong doors and locks to something with a roof that can be opened with a penknife.



I have not yet thought thouroughly about security. The roller door at the front will remain closed at most times and will probably have cabinets infront which will be on casters. I need to think about how the back doors (built by me) will lock securely. The windows in the doors will not be openable. The rooflights, if used, will need to be secured in someway. The workshop will also have an independant alarm system.


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## WellsWood

WiZeR":12c713bq said:


> I have infact decided to go with a solid sheet roof with maybe some rooflights or a dome. The main reason for this was the cost.



If you mean boarded and felted I know a great chap up in Thamesmead for roofing supplies. Cheap, friendly, and full of good advice, he also delivers the stuff to your door. Gave me the confidence to re-roof my own workshop last year - saved me a bundle.

Looks like you're all sorted then, I'd get stuck in if I were you before this good weather disappears!

Mark


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## wizer

sounds good Mark

What would I need? Just ply and felt? Not looked into this yet


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## WellsWood

I used these instructions. It's for flat roofs, but the principle is the same. Just a matter of getting the high bits overlapping the low bits - an oversimplification I know, but not rocket science by any stretch. With the money saved over twin/triple wall clear roofing you could fork out for a couple of nice velux or similar roof lights. Board the underside of the rafters (I think there's a white ceiling board you could use for this) and infill with rockwool - hey presto, bright, airey, and cosy.

Mark


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## OLD

Cladding i used this product its cement fibre so no maintenance a 3.6 m length was £6 + del. so less expensive than cedar might be good up against the fence etc if you click my www button you can see how it looks on a smaller building


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## wizer

cheers OLD, I hadn't thought about composite materials, Will deffinately look into it.


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## Anonymous

Dave R":3bpq0nha said:


> I think I would change the rafter joint up at the top of the high wall. As it is now, it looks like a split waiting to happen.



That was precisely my thoughts when I looked at the shketches. 



MarkW":3bpq0nha said:


> 1. I would definitely bolt the wall plate to the side of the house and use joist hangers. I have used this method a few times now on similar projects and they're all still standing. It will add considerably to the stability to have the whole thing attached firmly to the house.


 
The ridge board (not wall plate) _definately_ needs to be fixed sound to the wall to stop the wind ripping the shed off and/or distorting the structure and causing leak failures in the roof etc. I wouldnt cut little notches especially at the top end of the rafters, you reduce the strenght consuiderably. Also rafters should always go vertical not horizontal. I'd cut a simple plumb cut for the top of the rafter and a birdsmouthed plumb/seat at the wall plate end of the rafter, leaves overhang to get water away from the walls. And I wouldnt use joist hangers to fasten the rafter tops. They are to hang joists. I'd simply rawl bolt (or even use frame fixings) a ridge board to the wall and spike the rafter tops to it with gunbo nails. I just made a similar structure, very similar but not as big. The common rafters were only about 3x1 yet fixed as I described I could safely stand on one rafter. The wall plate was only 2x2 and wall studs 2x2 clad up with recycled 5/8 " shiplap boards. Hope this helps, hope it turns out all right!
Cheers Mr Spanton


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## Nick W

If its not too late. I've just been in my local Travis Perkins, and they're advertising a new, self adhesive, roofing felt system :shock: 

It is called Safe-Seal, made by Anderson Monarflex (Icopal), and they claim a minimum 20 year life expectancy. 'Fraid I don't know any more than that though.


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