Timber frames houses

[nobby]

The house I have just moved into is of timber frame construction. I've not had anything to do with this type of house before, but I've been told it is important not to damage the vapour barrier when doing any work.

How far is the vapour barrier behind the pasterboard? What would be the best way to run a cable down behind the plasterboard - I don't want to cut into the wall only to find I have cut through the vapour barrier (if I do, is it easy to fix?).

I will want to put a 4 inch cooker hood extractor pipe through the wall - does the vapour barrier need to be tightly sealed around this pipe?
The surveyor said if ever we had an extension or any major work we would need to use a builder experienced in timber frame houses - was the surveyor just being cautious or is there a serious risk of moisture getting in and rotting the frame?

Cheers,
Bob.

 

[jobalot]

Hi Bob,

I too have a timber frame house, and have done a little work on the internal and external walls.

I assume that the vapor barrier is located on warm side of the house; If it were not, in order to penetrate it, you would have to drill/cut through any wall insulation. THis makes sense as water vapour is more of a problem inside the house as opposed to outside due to breath, sweat, clothes drying, etc..

With the internal walls (say a bedroom adjoining a bedroom), I have found the only barrier as such is a silver themal foil attatched to the back-side of the plasterboard. I can see no prblem in perforating this; look around - there are probably already loads of holes for wall fittings, pictures etc i'ts pretty perforated as it is! I guess it is likley that this is where you will run your cable (ive done it!).

External walls, from my limited experience, seem to be the same. Again, it boils down to once you have drilled a hole through the plasterboard, stop. You cant actually drill any further, (unless you want to drill into the brick outer shell...very odd..) so even if there is a barrier of some kind there, you can try to avoid it.

But, even if you do manage to cut through a vapor barrier, unless the hole is the size of a plate, I dont think it would be a prblem - timber frame houses are well ventiliated (to keep the wood dry). And besides, it is only water vapour it is keeping out, not actuall water, like a dpc.

I think your surveyor was being very, very cautious.

Just thought of something, remove one of your wall socjkets, and have a peek..youll see any barriers/insulation present (hang on, a wall socket/ceiling light must, in itself be the biggest hole going!!)

James

 

[Geo-B]

Your vapour barrier is directly attached to the outside face of your kit ie. stapled to your OSB or Ply. The brickies then nail wall ties to this when laying the outer skin. So the layers are from the inside out: Gyproc, 4x2 frame covered with OSB or Ply & filled with rockwool or similar insulation (inner wall cavity), Breather membrane (vapour barrier), 50mm exterior cavity with ties for bricks & finally the bricks themselves. Obviously breaching the vapour barrier could cause damp if not done carefully.

 

[legs-akimbo]

Not quite right..... plasterboard internal lining... vapour check...stud framework and insulation... sheathing material... breather membrane ... ventillated cavity... masonary outer leaf.

 

[nobby]

Thanks for the advice guys. I think running cables should be OK - as you say James, I can always see how the existing cables have been routed.

Legs-akimbo - you seem to know how these things are constructed - to run a 4 inch pipe for an extractor fan can I simply drill through all of the layers with a core bit and then seal the vapour barrier round the pipe with some tape? What is the best thing to use?

Cheers,

Bob.