Wall & Roof Details.

[Dibs-h]

I decided to start a new thread as it's about possible options as opposed to the one that will actually go on\in the workshop.

My workshop is to be 7.5m long by 4.5m wide. I don't want a low ceiling inside - so initially thoughts were along the lines of raised tie trusses, but the lateral thrust on the long walls became a concern. Especially as the SE was now suggesting building the walls with 9 inch blocks laid on their sides. Or double skin.

What threw a spanner in the works is the B\C chap suggesting it would make a grand "Granny Flat". Which got me thinking that whilst I have no intention of moving in my liftetime - looking back, there was a time when I never thought I'd be moving out of where I lived before - so why not think ahead and if I sell up, it certainly would make it an attractive proposition to a potential buyer.

So back to the conundrum -

Walls - outer single skin blockwork, with 4x2 timber inner skin (insulated between studs, vapour barriers, membrane etc. where necessary).

Roof - the SE has suggested steel I beams at ridge level and at almost eaves, with these bearing the loads from the rafters, etc. These would rest on the "gable" ends, so those might be double skin (or I'm thinking more along the lines of piers). He said he'd make sure that the beams would resist the bending moments in the horizontal plane.

Or, put 2 Queen trusses (I think that's the correct phrase) in at 1/3 and 2/3 and then a traditional roof? Now I think it would nicer than just an anonymous board ceiling. Not to mention that if (and it's a big if) if we ever moved - it would look far less "industrial". Any thoughts\advice? Also I'd be expecting to put piers where the Queen trusses would go.

If one was to use Queen trusses - I would only need 2, so get them made or make them oneself?

 

[MikeG.]

Dibs,

don't let your structural engineer dictate this building!

Unless the external walls are acting as a retaining wall, there is no need for 9" blockwork walls on a building of this size.

Why are you proposing blockwork for the outer skin? I can't really see what this would achieve in normal circumstances.

What sort of roof covering (tiles, slates, thatch, sheeting etc) are you proposing for the building? A vaulted ceiling is so easy on a roof of this small size.

Does this building have any permissions, and if not, are you working to any drawings?

Mike

 

[Dibs-h]

Dibs,

don't let your structural engineer dictate this building!

Unless the external walls are acting as a retaining wall, there is no need for 9" blockwork walls on a building of this size.

Why are you proposing blockwork for the outer skin? I can't really see what this would achieve in normal circumstances.

What sort of roof covering (tiles, slates, thatch, sheeting etc) are you proposing for the building? A vaulted ceiling is so easy on a roof of this small size.

Does this building have any permissions, and if not, are you working to any drawings?

Mike

Mike

9" block walls - I agree, I'm not doing that.

The reason block was proposed - by me, if one is honest - is that the workshop is "attached" to a new garage on a sloping site,

(ignore the door in the gable elevation)

and I'm building right up to the boundary wall. It felt that being built out of predominantly non-combustible materials would ease the B\C aspects.

Also I'm in a Conservation area and the Conservation Officers had to be "negogiated with" interms of finish, blending in, etc. Further compounded by next door having a restrictive covenant on the strip of land in question & more importantly having the "teeth" to enforce it. Not that I would want it to go that far - lovely people, but the CoE are the actual owners.

So without writing a war & peace - blockwork construction, render with limestone chipings, reclaimed stone to main elevation (roadside) and rosemary clay tiles (reclaimed) and the door design - is ultimately what it took to get Planning, Conservation and the CofE to approve the building.

Also it blends in with the period of the property and after a few years should like a converted coach house that was built with the house.

The above drawing shows the side elavtions and below shows the plans,

The internal wall won't be happening tho, nor the door in the workshop gable.

Also there are going to be solar panels on the workshop roof for DHW - it's the only south facing roof we have and it's isn't overshadowed to any great degree, even by the house - i.e. contributing to the load.

I saw some of the pictures about the "Oak Library" and found myself looking at the roof\trusses and thinking they (Queen Trusses) do look nice.

Vaulted ceiling - my only concern is that for a 7.5m run with no internal walls, etc. unstability might be an issue. Or is this more perception than reality?. I suppose the SE is being supersafe, but I want supersafe with a lowercase s and not an uppercase S.

Cheers

Dibs.

 

[EddieJ]

Just a quick thought about your choice of reclaimed Rosemary tiles. Rosemary tiles can sit a bit too flat, obviously this isn't an issue if you are just after a straight forward cheap reclaimed nib tile, but they wouldn't be the tile of choice for any of my projects.

With ref to the "queen trussed roof" there are many variations of the same theme, some more complicated than others. Do you happen to have an image of your proposed version. It also looks as though your roof pitch is about 36 degree, so the proportions using a queen truss may look a bit weird and stunted.

Mike may be able to advise you further, but you could just construct a simple wooden ring beam a simple truss such as this one shown in the photo below. This frame was finished about two months ago, but by memory, the dimensions of the main frame, are pretty much the same as your proposed project. I see no reason why you should need the steel that your SE is pushing, but suspect that he isn't perhaps familiar with timber framing and steel presents less problems for him to calculate.

 

[Dibs-h]

Cheers Eddie - the choice of Rosemary Clays was something out of my control - the house is Rosemary Clays - and being in a conservation area, it was "required" if you see what I mean. Not to mention the existing garage that is going to be replaced has them.

Yes - the roof pitch is about 35-36 degrees. I haven't anything in mind at the moment other perhaps seeing the the roof in pictures on the "Oak Library" thread,

https://www.ukworkshop.co.uk/forums/view ... hp?t=33342

you can make out the trusses at the top of most of the photos - I'm not entirely sure what type of trusses they are.

In terms of the trusses I could use - I'm open to suggestions. In all fairness - the SE did say that one could use 2 large trusses at 1/3 and 2/3 or steel. I think he's looking for me to make a decision. And as I'm doing the steel for the foundations now - I have the luxury of a little time to choose the roof constructions.

Queen Trusses - after 5 mins on google - it appeared that those would be suitable for placing at 1/3 & 2/3 and then building the roof off those, but I'm sure other designs would be suitable, probably simpler ones - suggestions please?

In the picture you posted - the 2 trusses, from looking at the picture, I assume there are\will be 3 in total? Will there be some member going across the 3 trusses, a purlin perhaps? And then rafters from ridge board to wall plate, sitting on the purlin at mid-point? Would these rathers have birdsmouths where they sit on teh purlin and also at the wallplate?

Many Thanks.

 

[MikeG.]

Dibs,

I'll have a look at this either at lunchtime or this evening.

Mike

 

[EddieJ]

I retract my opinion about the queen truss not looking too good on a36 degree roof pitch. It suddenly occurred to me today that the build that I am currently constructing has both a 36 degree pitch and is 5000mm wide! Okay its 200mm wider than your build, but when I stood back and looked at the proportions and heights, I reckon that it could make a very nice feature for you. It is one of those things where the propotions look better in real life than they do when drawn up on paper.

If time permits, I may well make up a very quick softwood quick butt jointed one for you to gauge what you think.

I'm pushed for time right this second, but will elaborate a bit later in more detail about the photo that I posted.

 

[mickthetree]

Hi Eddie

Just a quick question - dont mean to pinch this post, but the closest corner showing the that photo....

the two sides sit with a lap joint on top of the corner post. Do you put a tenon on that upright corner post that passes up through the two lapped joints?

 

[Dibs-h]

I retract my opinion about the queen truss not looking too good on a36 degree roof pitch. It suddenly occurred to me today that the build that I am currently constructing has both a 36 degree pitch and is 5000mm wide! Okay its 200mm wider than your build, but when I stood back and looked at the proportions and heights, I reckon that it could make a very nice feature for you. It is one of those things where the propotions look better in real life than they do when drawn up on paper.

If time permits, I may well make up a very quick softwood quick butt jointed one for you to gauge what you think.

I'm pushed for time right this second, but will elaborate a bit later in more detail about the photo that I posted.

Cheers Eddie - How quck are they to make up - assuming I'm not after oak or anything? I'm just thinking ahead - schedules (mine) etc. Something one could do?

I'm probably about 2 weeks from having to finalise the design of the roof - i.e. before the walls start to go up. Photo - cool, no rush. I think I may have to go and get me book or something or trusses, roofs, etc.

 

[MikeG.]

Dibs,

unless your walls are acting as retaining walls, then they don't need to be of blockwork. I would advocate building a studwork wall on a low brick (or stone) plinth, and you can have the same rendered finish on the outside as you were proposing with blocks. The huge difference is that the thickness of the wall can be filled with insulation, whereas with blocks you have 4" (or, god help us, 9 inches) of wall plus any insualtion.

Doing it my way will result in 10 inches more floor space compared with your engineer's proposal, and that is before you have insulated the blockwork. That would be another 2.5 inches each side at least.....so my way would save you 15 inches of width the entire length of the building (as well as a small fortune in materials).

The roof is easy. A couple of principal trusses (as in the photos, or cheaper simple soft wood trusses), a structural ridge beam (AKA a ridge purlin), or orthodox purlins (more complicated) and infil with common joists. A doddle. Or you could do a raised tie cut roof, or raised tie trusses, and have 2 or 3 or 4 ties across between the wall plates.

My over-arching advice is to forget completely the idea of 9" blockwork walls........rarely have I heard anything so silly. This is barely bigger than a single garage, and goodness, there are plenty of those built in 4 inch brickwork.

If you want to talk this through, PM me for my phone number and we'll have a quick chat.

Cheers

Mike

 

[promhandicam]

Dibs,

unless your walls are acting as retaining walls, then they don't need to be of blockwork. I would advocate building a studwork wall on a low brick (or stone) plinth, and you can have the same rendered finish on the outside as you were proposing with blocks. . . .Mike

Mike,

Sorry to hijack this but what would you use on the outside skin of the stud wall to then render? Would this still be ok within 1m of a boundry as it has to be substantially non combustible?

Cheers,

Steve

 

[MikeG.]

Steve,

I would batten out, then use EML (expanded metal lath) over building paper (to prevent the render pushing through the lath endlessly). This will work fine so long as the cavity thus formed is ventilated, which is really easy.

Mike

 

[EddieJ]

Dibs, for some reason I had thought that your building was 4.8m wide, when in fact it is 4.5m. I have so many figures going through my head, that I slipped up! :roll: Anyway, I still reckon that it could work, but I'll take a photo tomorrow for you of how the frame looks as a conventional cut and pitched roof with horizontal collars and diagonal wind bracing.
If you have access to a bandsaw, I can come up with a design of wind bracing that's called 'Donkey Leg' A photo will show it better than I can explain it, so I'll sort one out for you tomorrow.

Dibbs in answer to your question about a third truss, in my opinion the whole design of the frame was pretty ill thought out, and there wasn't a third one. The photo below shows how it was finished prior to having the warm roof and sprockets put on.

I'll delete the following photo tomorrow to avoid side tracking your thread even further!

I also apologize for the following shot and will also delete this one tomorrow.
In answer to the question raised by mickthe tree. The corner half laps were also tennoned, as can be seen the photo below that shows part of my trial frame erection in the workshop.

 

[Dibs-h]

Mike

9" walls - dear God, I'd resist that with some fervour!

Timber walls - I'll have a bit of a ponder on that. When the original idea was to attach the workshop to the end of the existing garage which is 2.8m wide - getting an extra 6" would certainly be noticeable. But now the total floor space is likely to be over 50 sqm. 12.5m x 4.2m (maybe a little wider) for the workshop and a 6m x 4.2m full height basement under the garage, so loosing 6" in width, isn't so worrying anymore.

Roof - that's exactly what I wanted to hear. More and more, I am erring towards a pair of principal trusses and perhaps purlins in between and infill with joists. I think it would add character to the building.

Many thanks for the offer of a chat - I'll certainly take you up on that.

Eddie - please leave the photos, it's not sidetracking the thread. All good info. The lack of a 3rd truss - I see it now, hipped end. There don't seem to be any purlins between the trusses? I take it they aren't needed - in this case?

I do have a band saw - but it's a Dewalt with a 155m cutting depth.

I do like the idea of 2 principal trusses with purlins and joist infill. Would the purlins sit proud of the truss or could they be notched into the truss and therefore flush?

Many Thanks.

 

[Dibs-h]

Eddie

I was think something along the lines of Douglas Fir or even seeing what the local timber reclamation yard has interms of old joists and purlins and use them.

The span from the external blockwork faces is approx 4.1m, from the inner faces will be 3.65m as the trusses will be sat on piers. The roof angle is around 35degrees. I'm expecting a roof overhang of around 8".

What sort of timber sizes will I require? Any good book\s you can suggest?

Also any details on the construction of them from a joint perpective? M&T and pegs spring to mind but that's all & even that's just at a general level.

The Principal trusses you show in the picture - I like the look of them. Are there any other design options for trusses or is that it really.

If I was to make them - how long do you think each one might take?

Dibs

p.s. Just realised I already had a thread on roof details - so just deleted the other one.