Vapour barrier plaster boards

[cooperphilip]

I have just boarded nearly all my loft with foil back plaster boards . I have ran out of the foil back plaster boards and have a piece of about 2ft squared to complete the job. I have got some standard board what will fit and some polythene vapour barrier left. Would it be ok to staple the barrier sheet to the back of the plaster board and then use it ?

 

[roughcaster]

I'm not too sure about this one. With foil backed plasterboard, the foil itself, is attached/manufactured to the board as you know. But stapleing a barrier sheet onto the back of a plain sheet of plasterboard, mmm, I suppose in theory it would/should work. Even if you stapled a barrier sheet across the studs and then fixed the plain p/boards, that would be be the same thing..... Anybody else have any views on this one.

Roughcaster.

 

[Bondai]

Plaster boards are supposed to be fire retardent and the poly sheet will render it flamable.

Another point. Common sense tells me moisture could possibly build up between the poly sheet and the board.

Much better idea is to go get some more of the foil backed. Better be safe than sorry.

 

[Richard C]

For christ sake, get another foil backed board & be done with it, you know it makes sense . Does it make any sense to compromise the good work you’ve already done in your loft for under a tenner even at the extrotionate prices some may charge!

 

[roughcaster]

Plaster boards are supposed to be fire retardent and the poly sheet will render it flamable.

Another point. Common sense tells me moisture could possibly build up between the poly sheet and the board.

Much better idea is to go get some more of the foil backed. Better be safe than sorry

.

I think so too, that way you're sure it's been done properly, and for all the cost of a few extra sheets.

Roughcaster.

 

[stuart45]

Polythene vapour check is used behind the plasterboard on timber framed houses, so the fire risk and moisture problem would be the same on these.

 

[^woody^]

Use the polyhene - it will do the exact same job as the foil

It wont affect the fire rating in the slightest

Why buy more materials to use a bit and then throw the rest away - arn't we supposed to be thinking about the waste nowadays?

Use what you have, your original idea was sensible

 

[andyandy2]

Why not glue the polythene to the plsterboard, or you could try gluing some kitchen foil on

 

[cooperphilip]

Ok thanks for advice.

Also the internal walls in the loft right underneath the big 9 x 2 eaves. I have put one side up of the wall and am about to insulate with lagging and then put the back wall up.

I have been told I need a vapour barrier here and I done.

Any Help ?

Also if I do where do you put it as so to speak there is no real cold side and do you need a airgap on internal walls ?

 

[cooperphilip]

Plaster boards are supposed to be fire retardent and the poly sheet will render it flamable.

Another point. Common sense tells me moisture could possibly build up between the poly sheet and the board.

Much better idea is to go get some more of the foil backed. Better be safe than sorry.

How can that be if you can use polythene as a vapour barrier. for e.g if you get sound proof plasterboard then and you need a vapour barrier you need to use a plastic barrier no matter what.

 

[stuart45]

Anyone that has ever tried to burn plasterboard will tell you that it would take more than a bit of polythene to set it alight. The only slight advantage with foil backed plasterboard is that insulates better with radiant heat, but the area you are talking about is too small to worry about.

 

[ratman123]

Vapour barriers are used where there is a warm and cold side, and the barrier is always put on the warm side.

If there is no warm/cold side, then i don't think you need it.

 

[cooperphilip]

Yes I am unsure though whether the side walls under the 9 x 2 eaves has a cold sir.

It is directly under the shallow part of the roof which is cold in a way.