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Evening all

PostPosted: 21 May 2019, 21:51
by arf03
Hello everyone.
Found this site a number of weeks and have spent some considerable time reading many (probably too many) posts. I am about to start a smallish workshop build and I have already gained a vast amount of information from this site. I am reasonably confident at home improvement , hard landscaping etc etc . Workshop is going to be approx 4.2m x 2.8m (2.5m tall) with a pent roof. I am following Mike Gs build with a concrete base and 2 courses of brickwork. walls outside to inside will be cedral cement fibre board on counter batons, breathable timber frame membrane on 100 x 47 wall studs at 400 centres, insulation then 11mm osb on the inside. I have a question about the roof: I am going to cover it with an adhesive rubber edpm on top of osb board, what thickness of osb would people recommend ? and would I need to leave expansion gaps between the boards on the roof ? just concerned if I do this, will the edpm sink into these gaps. roof rafters will be 150mm x 47mm at 400 centres. any advice would be much appreciated, thank you. I am sure I will have many more questions yet. Brace yourselves :| Al

Re: Evening all

PostPosted: 22 May 2019, 07:21
by StevieB
Welcome!

Are you ever going to walk on the roof? I would say 11mm is fine on the 400 centres you propose, 18mm if you really want to, but OSB is heavy so think about how you will get it up there and how you will move it around when it is up there.

In terms of expansion gaps, most advice is to leave 2-3mm, or the width of a saw kerf, for expansion. OSB will not expand that much due to its structure, but it can get quite hot in direct sunlight under a black EPDM surface so well worth a small gap. Most people just stick a nail between the sheets to get the gap right then remove the nail when the next sheet is up and secured. Your sheet edge will fall on a rafter, so put up the first sheet, tap a nail into the rafter but leave it well proud of the sheet, then run the next sheet up to the nail.I wouldn't worry at all about EPDM sinking into a 3mm gap, it is not that flexible!

We do like pics, so remember to take lots as you build - it also makes it easier to answer questions if you have any :D

Re: Evening all

PostPosted: 22 May 2019, 07:31
by Mike G
Welcome Al.

Steve has given you most of your answers, and I've nothing to quibble with in what he said. I would add a couple of things, though, and start by saving you some money and some work. Unless there is something going on which you haven't mentioned, you can do your studwork and your rafters at 600 C's. In fact, with such a small building, you could do your studwork out of 3x2s (70x45 CLS) at 600 C's, and then use 9mm OSB internally.

I would definitely plump for 18mm OSB on the roof, though. Anything thinner is likely to sag over time between the rafters.

Re: Evening all

PostPosted: 22 May 2019, 07:39
by Andyp
Welcome Al, the spam trap will stop you posting pics until you have made 3 posts, after that the more the merrier.
What will you do in this workshop once completed?

Re: Evening all

PostPosted: 22 May 2019, 08:03
by arf03
Thanks for the quick responses, appreciate that. I am up for anything that saves me money Mike ! so will take your advice on the studs etc @ 600 centres. Any preference on the best timber frame breather membrane to use ? Base is under way, will post some pics in the next few days.
Thanks, Al.

Re: Evening all

PostPosted: 22 May 2019, 08:11
by Mike G
The best? No idea. I normally go on price! You can probably pick up half a roll on Ebay or the like, rather than buying a load and wasting it. Roof membrane works perfectly well for the walls, too.

Re: Evening all

PostPosted: 22 May 2019, 09:10
by Malc2098
Evening, Al.

(I sound like George Dixon there!)

Welcome from deepest Mid-Devon.

Re: Evening all

PostPosted: 22 May 2019, 10:46
by TrimTheKing
Hi Al and welcome aboard.

I can't add anything to what the guys have said, except please bring us along on your build journey with pics and words as all these builds help create a great resource for our members and anyone who hasn't yet found us.

Re: Evening all

PostPosted: 22 May 2019, 21:08
by MY63
Hi Al welcome
I have just finished my shell and I am pleased to say it went reasonably well it was my first major project. In fact the first real diy job for many years. The support here made it possible and I am proud of the result.
I have just fitted my EDPM roof and had forgot about the gaps so I crawled around the roof with a cordless circular saw and cut in the gaps my EDPM did not sink into the gaps.
Can’t wait to see your progress.

Re: Evening all

PostPosted: 24 May 2019, 15:15
by tabs
Hi al,

doing very similiar build and size to you. Only got to put the cladding on now. I used 18mm osb on top of the joists with nail used to set a gap. I then insulated on top of the boards and epdm over this.

Re: Evening all

PostPosted: 25 May 2019, 09:28
by Phil
Welcome from very far down South. :D

Re: Evening all

PostPosted: 26 May 2019, 11:49
by arf03
Thanks again for all the welcome messages and advice so far. It is a misty murky day down here on the North Cornwall coast, so I thought I would get a list of materials together for the shed / workshop build.
Thinking about the roof ( as mentioned it will be a pent roof with edpm on top), can I build all walls to same height and then use 'firring strips' to get the fall from front to back ? I think the firring strips are 50mm thick tapering to nothing, this would be over a 2.8m span across the roof, what do you guys think ??
Cheers,
Al.

Re: Evening all

PostPosted: 26 May 2019, 11:51
by arf03
MY63 wrote:Hi Al welcome
I have just finished my shell and I am pleased to say it went reasonably well it was my first major project. In fact the first real diy job for many years. The support here made it possible and I am proud of the result.
I have just fitted my EDPM roof and had forgot about the gaps so I crawled around the roof with a cordless circular saw and cut in the gaps my EDPM did not sink into the gaps.
Can’t wait to see your progress.


Thanks, will definitely leave a gap.
Al.