External timber frame wall

spudgobbler

Hi all.
I have a question that I want to ask. I only want answers from guys whom have tried this before and what was their experience with it.
I don’t want answers from guys who sit behind a computer and over spec everything in carpentry these days. I’m 20 years in roofing and extensions myself but this is a new journey for me.
I’m doing a timber frame extension, it’s consists of 6x2 stud, 3/4 osb on the outside of that then it’s wrapped with breathable felt, on top of that is riblath followed by plaster. If I use a breathable earthwool and a 3” insulated slab on the inside will I run into mold or dampness problems.
I visited an old builder whom did the exact same thing over twenty years ago and he hasn’t had an issue ever. I inspected a few spots on his extension and found it to be bone dry throughout with no issues.
Has any one tried this before.
Kind regards
Steve

Calahonda52

I am sitting behind a computer so my contribution will not be welcomed so don't read it: its for others to benefit from.

If the render is cement based and the 3" slab has alu facing on it then, with a gypsum based skim on alu faced pb: then
for south facing walls, solar drive will be an issue

spudgobbler

Please don’t be insulted I didn’t mean it like that all comments and advice are welcome.
If I cross batten the interior of stud then put 4” of insulated plasterboard on top of that would that allow moisture escape. Obviously I’d Have to bore for vents
Kind regards
Steve

BryanF

spudgobbler wrote: »

Hi all.
I have a question that I want to ask. I only want answers from guys whom have tried this before and what was their experience with it.
I don’t want answers from guys who sit behind a computer and over spec everything in carpentry these days. I’m 20 years in roofing and extensions myself but this is a new journey for me.
I’m doing a timber frame extension, it’s consists of 6x2 stud, 3/4 osb on the outside of that then it’s wrapped with breathable felt, on top of that is riblath followed by plaster. If I use a breathable earthwool and a 3” insulated slab on the inside will I run into mold or dampness problems.
I visited an old builder whom did the exact same thing over twenty years ago and he hasn’t had an issue ever. I inspected a few spots on his extension and found it to be bone dry throughout with no issues.
Has any one tried this before.
Kind regards
Steve

I spec timber frame and sit behind a computer: so don’t bother reading if you don’t want..

In my extension I double battened and put cement fibre board outside the breathable felt.

The rule of thumb for insulation to avoid interstitial condensation is to keep 2/3 insulation outside the vapor barrier

Insulated slabs are not breathable

spudgobbler wrote: »

Please don’t be insulted I didn’t mean it like that all comments and advice are welcome.
If I cross batten the interior of stud then put 4” of insulated plasterboard on top of that would that allow moisture escape. Obviously I’d Have to bore for vents
Kind regards
Steve

If you bore vents doesn’t that negate the insulation?