Garage conversion studwork advice
- Thread starter wackpac
- Start date
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Local BC guidance details 60mm pir or 90mm rockwool.
on the warm side?
what do you think of the vapour barrier (tyvek) on the cold side?
What does the guidance say about pattern staining on the inner face of the timber?
That's why I am planning to use PIR sheeting over the front of stud wall - would this not address that issue
I've planning 100mm Rockwool between and 20-30 PIR over - is that ok
Yes it would.
But what I was alluding to, is that you posted an image from I don't know where and is this supposed to be "guidance"? If it is it is clearly misleading guidance as it does not describe how to deal with pattern staining. So what else is not very good guidance from that bit of guidance? The cavity perhaps? No weep holes in the cavity? The cold bridge from the floor joists? The floor air void? No vapour check on the warm side of the wall ? And yet it may comply with building regs.
it's crazy how much variation there is - the image I posted was addressing goncg69's comment that Rockwool can't be used in stud walls.
The image was from LABC's own website for garage conversion guidance.
I do appreciate the replies. Do you concur with goncg69 about the rockwool or is it a non issue? What do you think about my vDPM amendment I posted about
There are many ways to conform the building regs. Your inspector has given you one and that drawing may well be another.
When I do conversions, I work on the basis that the garage is already narrow and so space is a premium, so I don't want to build a wall thicker than it needs to be.
I'd work to principles of stopping damp coming in the wall and up the floor (vDPM and hDPM) well insulated and thin inner linings (tight up to the wall) and removing cold bridges (continuous insulation).
If you search the many threads, I'm sure the options and details are there. I know I've even posted a diagram of how to deal with a common central pier.
I'm not sure the thickness of PIR since the June update, but it used to be 60mm Celotex. However, whilst that passed regs it was only if it was continuous (not in between studs) and that did not allow for any services cut int to the wall. So a better target was to thicken the whole insulation to allow for services (80mm) or calculate how much should go between studs and then across the inner face.
Gonch mentioned 100 between and 20 over, but that was the pre-June spec for extensions (actually just 100mm between complied), and garages could be less. Again, I'm referring to pre-June so you would need to check what is required now - it may be much more onerous. Gonch may be correct regarding using Knauf quilt - that is for masonry walls with an inner skin of thermal blocks - which you won't have here, and it comes down to whether the 20mm of PIR is equivalent to the 100 or 120mm of thermal blocks. But either way, 20mm of PIR over a stud is not very good.
If you are not going to go with your inspectors' recommendations, then you need to propose a suitable detail and let them agree it. If you work on the principles above, then it can't be rejected.
When I do conversions, I work on the basis that the garage is already narrow and so space is a premium, so I don't want to build a wall thicker than it needs to be.
I'd work to principles of stopping damp coming in the wall and up the floor (vDPM and hDPM) well insulated and thin inner linings (tight up to the wall) and removing cold bridges (continuous insulation).
If you search the many threads, I'm sure the options and details are there. I know I've even posted a diagram of how to deal with a common central pier.
I'm not sure the thickness of PIR since the June update, but it used to be 60mm Celotex. However, whilst that passed regs it was only if it was continuous (not in between studs) and that did not allow for any services cut int to the wall. So a better target was to thicken the whole insulation to allow for services (80mm) or calculate how much should go between studs and then across the inner face.
Gonch mentioned 100 between and 20 over, but that was the pre-June spec for extensions (actually just 100mm between complied), and garages could be less. Again, I'm referring to pre-June so you would need to check what is required now - it may be much more onerous. Gonch may be correct regarding using Knauf quilt - that is for masonry walls with an inner skin of thermal blocks - which you won't have here, and it comes down to whether the 20mm of PIR is equivalent to the 100 or 120mm of thermal blocks. But either way, 20mm of PIR over a stud is not very good.
If you are not going to go with your inspectors' recommendations, then you need to propose a suitable detail and let them agree it. If you work on the principles above, then it can't be rejected.
I get your method of saving space is handy. But if the my guy said I need a cavity between 20-50mm I guess I need to go down that road. the cavity helps with leveling the piers so not such a bad thing. but now addressing having a non vented cavity? can I do liquid dpm on wall or hang vdpm down wall ? I may change to 85mm rigid pir between studs and 25 over.
any other input pls chaps
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