# New workshop build



## gerard b (8 Jun 2020)

Good evening all,

I'm a long time lurker but only now getting around to contributing (hopefully). I'm in the planning stages for a while now and have a few questions I'm hoping some of you fine people can help me with.

I'm a reasonably competent all round diy'er and this will be a 1 man self build but some of the detail has me a bit stumped at the moment.

Structure is going to be 9.6m by 4.8m outside measurements. 2x4 stud framed walls with a flat epdm roof. and larch clad. My first question is around the stud spacing. I'm thinking 400mm on centre, with 18mm OSB on the inside as lining as well as acting as a vapour barrier. The OSB comes in measurements of 2440x1220mm. Does this work for 400mm centres, I mean in regards the sheets lining up half way over each stud? Hope this makes sense to someone lol...


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## Doug71 (8 Jun 2020)

Sheets like plywood and OSB are still in imperial sizes 8' x 4' (2440x1220) but other things like plasterboard are metric so 2400x1200 #-o 

In the old days studs were set at 16" centres because everything was imperial. These days it's normally 400mm centres to allow for metric size boards, you have to trim the imperial size boards to fit.

Bear in mind your timbers will be metric lengths for example 4.8m which a bit shorter then 16'.

People tend to work in metric and trim the sheets to size, the sheets are often not perfectly square or bang on size anyway.


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## MikeG. (8 Jun 2020)

Hi and welcome.

For a start, this building will require Building Regs approval, which is a game changer. That means orthodox foundations, or a structurally engineered raft. It may or may not need to comply with Part L regimes, depending on whether or how you plan to heat it and so on. The typical structure linked to in my signature will not be in compliance. Your costs will be much higher than most of the workshop builds here, which probably average £125 to £175 per square metre.

If there is any way to build this as two separate buildings with neither over 30 sq internally, then you can avoid Building Regs.

As for your questions.......

Treat the nominal stud spacing as a guide, and alter it to suit your sheathing boards. 18mm OSB is fearsomely heavy, and not necessary for strength in the walls. Most people use 9 or 11mm. 600 centres is perfectly possible for a workshop, but this affects your wall plate or roof design.


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## DBT85 (8 Jun 2020)

Good luck!

I made my plans and Fusion mocukup in such a way that I can change it if the sheet gods for some reason turn up in 1220 or 1200. I've seen some people get half of one size and half of the other!

Mike knows everything, but buy all means pop in to my build thread and see what I've been upto. Much of what you want may be in there already. Or in any of the dozens of others!

My only question is why the flat roof over a pitched roof?


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## gerard b (8 Jun 2020)

Hi guys and thanks very much for the prompt replies.

So if my sheets are 2440x1220 I go with 16” centres and if they’re 2400x1200 I go with 400mm on centre? That makes sense I think. 

Mike, I was going 16” or 400mm centres as I thought that would be best for structural strength with 9x2’s on the roof. I’ll be going with a warm roof. I think you’re right on the 18mm osb, 11mm will be fine.


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## gerard b (8 Jun 2020)

DBT85, thanks I look forward to checking out your build. 

The flat roof I figure is just easier, this is a daunting enough project as it is lol... it also makes more sense for what I’ve planned to use the inside space for. I just find there’s a lot of wasted space in a pent roof too.


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## MikeG. (9 Jun 2020)

gerard b":19r5rmtl said:


> ......... I just find there’s a lot of wasted space in a pent roof too.



You don't mean pent roof, I reckon. You mean a pitched roof. A pent roof is a misused term at the best of times, as it is built against an abutment wall (or two). You are proposing a flat roof or a mono-pitched roof. The upside of a flat roof is easier construction. The downside is that it is uglier than a pitched roof. The "wasted space" you talk about in a pitched roof is wonderful storage, and also a good place to run ducting if you have an extraction system. Indeed, some people put the whole system up there. Mine is absolutely chocker block with wood.

Whilst on the subject of rooves, you do realise that you are going to end up with a roof which is about 400mm thick, don't you? That's what a warm roof does. I can only assume you have planning permission for this building, because otherwise you are going to struggle to fit under the 2.5m height limit for Permitted Developments because of the warm roof choice.

You haven't answered the point about the size of your building and building regulations. You are going down the route of a 1m+ dig for foundations (or structural engineers fees and a massive raft), cavity walls, and council inspections. Why?


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## DBT85 (9 Jun 2020)

gerard b":l6ps2ajg said:


> DBT85, thanks I look forward to checking out your build.
> 
> The flat roof I figure is just easier, this is a daunting enough project as it is lol... it also makes more sense for what I’ve planned to use the inside space for. I just find there’s a lot of wasted space in a pent roof too.


You sound like you have a similar DIY experience to myself. Have a watch of some videos about cutting rafters, it's not too hard.

The reason I went with a pitched roof was for headroom over anything. One 3m section of my workshop will have nearly 3.5m from floor to the middle of the ceiling, while with raised ties the rest of the ceiling will be around 2.5m.

That's hard to do with a flat roof and the 2.5m eaves height rules as you need thick rafters to span the kind of gap you are talking about.

Another note, 600mm centres works fine.


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## gerard b (9 Jun 2020)

Hi Mike, yes I mean pitched roof and the flat roof is purely for simplicity for me. I've got nowhere near the skills most of you guys on here have and no doubt I'll have to make some compromises along the way.

I live in a very rural part of Ireland, miles from any other dwellings so planning is not an issue.

Thanks again for all your help so far guys, very much appreciated.


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## gerard b (9 Jun 2020)

@DBT85, I read through all of your build so far just lat night, brilliant I really enjoyed it, it's going great.


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## gerard b (9 Jun 2020)

By the way guys, how long is it before you get permissions to send private messages on here?


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## gerard b (9 Jun 2020)

Ignore that, I have access now, you must have had to have a certain amount of posts before you got pm privileges.


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## gerard b (15 Jun 2020)

Well I got the base in, unfortunately I haven't figured out how to add pictures here yet, I think the file size is too big. Anyway base consists of compacted hardcore, sand blinding, dpm, 100mm board insulation followed by 5" of concrete pour.

Thinking ahead to the wall framing and the roof, I'm still trying to figure out how to put the slope on the flat roof. I was thinking of making furring strips as this seems to be the simplest method. Is this practical though over a span of 5mtrs?


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## DBT85 (15 Jun 2020)

Do you have your images uploaded anywhere or are they only on your machine? You can either upload to a host like Flickr like I do or upload to the forum itself.

Them you'd post the image by putting in its hyperlink like this. Just remove the * I've added in. 

[*img] image url here [/img]


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## MikeG. (15 Jun 2020)

Yes, firring pieces are the standard way of producing a fall.

A 5m span, though, is not a great idea. With overhangs this means you are going to be looking for roof timbers of 5.4m, and around here that is a special order, and pricey. It also means your roof timbers need to be 250 thick. With firring, insulation and two layers of board that means a roof some 450mm thick if you do a warm roof.


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## DBT85 (15 Jun 2020)

Davies timber who I got my ridge from carry that kind of size as standard I think. But most won't.

Go pitched. Can't be that hard, I'm doing it tomorrow!


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## gerard b (15 Jun 2020)




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## DBT85 (15 Jun 2020)

Ah, to share flom Flickr your want to click the share button, it's a little sort of up and right arrow in the bottom right corner. You then want to select bbcode as the format to share.


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## gerard b (15 Jun 2020)

MikeG.":26itckai said:


> Yes, firring pieces are the standard way of producing a fall.
> 
> A 5m span, though, is not a great idea. With overhangs this means you are going to be looking for roof timbers of 5.4m, and around here that is a special order, and pricey. It also means your roof timbers need to be 250 thick. With firring, insulation and two layers of board that means a roof some 450mm thick if you do a warm roof.



Plan was to go with 9x2’s (220mm) and they come in 5.4m lengths where I’m buying my timber, above that size and as you say, they get pricey.

Is it just a matter of doing a taper cut the full length of the 9x2 to make the firring strips?


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## gerard b (16 Jun 2020)

CDC21AE0-F7F7-481C-A8C0-A4354C1C4B02 by Gerard Barrett, on Flickr


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## gerard b (16 Jun 2020)

662EF173-9AC9-4540-B883-FE13F3241091 by Gerard Barrett, on Flickr



72FADF2C-82B9-45B0-831E-2C4D3B978AFE by Gerard Barrett, on Flickr


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## gerard b (16 Jun 2020)

Well I figured out how to do pictures  thanks to DBT85 for the help.


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## DBT85 (16 Jun 2020)

No problem! looking like a good start!


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## MikeG. (16 Jun 2020)

gerard b":1y3qhqcc said:


> .......Plan was to go with 9x2’s (220mm) and they come in 5.4m lengths where I’m buying my timber, above that size and as you say, they get pricey.



My tables suggest that isn't strong enough. Your choice.



> Is it just a matter of doing a taper cut the full length of the 9x2 to make the firring strips?



Yep, that's it. You essentially cut long thin wedges and nail them on top of the joists.


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## gerard b (16 Jun 2020)

MikeG.":2oj17i9h said:


> gerard b":2oj17i9h said:
> 
> 
> > .......Plan was to go with 9x2’s (220mm) and they come in 5.4m lengths where I’m buying my timber, above that size and as you say, they get pricey.



My tables suggest that isn't strong enough. Your choice.

Thanks Mike, if that's the case, it's just going to have to be 10x2's.

With regards the firring strips, could you do it with a circular saw? I'm thinking 60:1 for the fall (or would 80:1 be ok). Could you just run down a length of 10x2 with the circular saw to get the taper. Any idea what height i'd need to do, i.e from what height tapered down to zero?


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## MikeG. (16 Jun 2020)

No, you can't subtract from the joists. You have to add to them. Cutting the slope into them will weaken them (and remove the treatment as a secondary problem).


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## gerard b (16 Jun 2020)

MikeG.":2n4rgrlj said:


> No, you can't subtract from the joists. You have to add to them. Cutting the slope into them will weaken them (and remove the treatment as a secondary problem).



Sorry Mike, I didn't explain that very well. I didn't mean I would taper cut the actual roof joists. I meant using another 9x2 (or whatever size is required) to cut the firring strips from, then attach these firring strips to the top of the joists.


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## DBT85 (16 Jun 2020)

Gerard, are you building this to be 2.5m at the eaves and under 3m total, or under 2.5m total?

EDIt: never mind, i recall planning is not an issue for you. 

Still. I cut all 26 rafters for mine today. It's really not too hard and you'd have so much more volume to work in.


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## Fil (16 Jun 2020)

Gerard is that concrete a recent job done? Can i ask how much yoi paid per m3?

Only asking as it was around £100 pre covid, beat price seems to be £165 now. Thats for the mix on site stuff, rather than arives pre mixed, thats a bit less anyways

Im east london / essex area.


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## gerard b (16 Jun 2020)

Overall height at the moment I’ve got at 2967, that’s without the firring strips. I have to work out how to measure those to get the desired fall.

Got a call from timber yelled today though to say there is a delay with my order, it was supposed to be here today but looking like next Monday now. On the plus side, the nailer arrived yesterday.


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## gerard b (16 Jun 2020)

Fil":ua7ipno7 said:


> Gerard is that concrete a recent job done? Can i ask how much yoi paid per m3?
> 
> Only asking as it was around £100 pre covid, beat price seems to be £165 now. Thats for the mix on site stuff, rather than arives pre mixed, thats a bit less anyways
> 
> Im east london / essex area.



Well I’m in Ireland so not much use to you. It was €90 per cubic metre.


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## DBT85 (16 Jun 2020)

Fil":2u4fiy26 said:


> Gerard is that concrete a recent job done? Can i ask how much yoi paid per m3?
> 
> Only asking as it was around £100 pre covid, beat price seems to be £165 now. Thats for the mix on site stuff, rather than arives pre mixed, thats a bit less anyways
> 
> Im east london / essex area.


£100 a cube sounds cheap unless it's the ex vat price. Mine ran to about £135 Inc vat. Most quotes I had were about the same but I'm in the Midlands.


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## gerard b (18 Jun 2020)

I was reading through Steve Maskery's brilliant workshop build thread the last few days and came across his square of Thales. Since I'm still waiting for my timber to arrive, I decide to make one and what a great tool it is. I think it's going to be of great assistance when it comes to layout and getting everything square.


3CD5E3A7-CAB8-425C-98D3-135C9D63D53F by Gerard Barrett, on Flickr


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## DBT85 (18 Jun 2020)

It certainly has its uses but when you start framing you only need to get it mostly square on the floor, nail it together and then measure the diagonals to get it bang on, then secure it with some sheet material or a batten. Thales square will be good for sorting out other bits.


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## gerard b (18 Jun 2020)

DBT85":3gmsanfj said:


> It certainly has its uses but when you start framing you only need to get it mostly square on the floor, nail it together and then measure the diagonals to get it bang on, then secure it with some sheet material or a batten. Thales square will be good for sorting out other bits.



I was thinking it would be most use when getting the bottom plate square. I'll be using a double bottom plate with the first plate anchored into the concrete (I know a brick plinth is better :wink: ) but this is how I decide to go, it'll have a dpm under it and the cladding will extend below it.


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## DBT85 (18 Jun 2020)

Still better to just measure the diagonals. If you know your timbers are the correct length then if the diagonals match its done.

Yhe diagonals at least measure over the entire distance covered, bit just the length of your Thales.

I wish you luck, with cladding and plates that close to the ground your workshop might not last as long as you would hope!


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## gerard b (10 Jul 2020)

Well it's been a while since my last update but I've made some progress in the last couple of weeks. Weather has been rubbish and I'm working on my own but here I've got the walls framed out and erected.



IMG-5077 by Gerard Barrett, on Flickr 

Here is with the roof timbers going up.



IMG-5080 by Gerard Barrett, on Flickr

These 2 pics show the roof timbers all up including the noggins (think that's what they're called). 



IMG-5086 by Gerard Barrett, on Flickr



IMG-5087 by Gerard Barrett, on Flickr

Fascia boards are next up and then I've got to somehow get 32 sheets of osb up there on my own. I think I should probably put at least some sheets of osb on the walls first just to give the structure some rigidity before I start climbing up on the roof.

Hopefully I'll have some further updates after the weekend, if the weather stays dry.


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## gerard b (10 Jul 2020)

I decided to go with sloped walls rather than the firring strips on the roof. It was actually much easier than I thought. I just marked the walls up with chalk lines on the floor and then lined up and cut my studs from this.


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## MikeG. (10 Jul 2020)

Walls straight on the concrete. Why oh why do people do this?


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## gerard b (10 Jul 2020)

MikeG.":3oxhh4cf said:


> Walls straight on the concrete. Why oh why do people do this?



I was pretty much expecting this comment and was reluctant to even do an update, sorry I did now, I think I'll leave it at that.


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## siggy_7 (10 Jul 2020)

Looks smart to me, would love to have a space like that even if the wall isn't to best practice. 

Sent from my SM-N960F using Tapatalk


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## DBT85 (10 Jul 2020)

Looking neat Gerard, Keep it up!


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