Vapour barrier in loft conversion...

[Adam]

Hi All,

We're in the process of insulating our loft conversion, something the builders that performed the conversion didn't seem to think was necessary - in Scotland. To do this we've been taking down the plasterboard on the walls and pitched part of the ceilings and putting XtraTherm (which appears to be a Celotex clone) between the studs. This is an old stone house with wooden rafters forming a pitched, slated roof.

First room we did was the bathroom and f*ck me if we weren't too stupid to remember to put a vapour barrier in before putting the new plasterboard up over the insulation. D'Oh!

I guess we really need to get some vapour barrier in. Is there an alternative to pulling out the plasterboard, stapling up polythene and putting the more plasterboard up?

Replies don't have to be sypathetic.

Cheers - Adam...

[Tony Bryer]

2 coats of Gyproc drywall sealer, according to its manufacturer will provide a vapour control layer. I suspect that a couple of good coats of vinyl emulsion would too.

[fred]

In article , Adam writes

Wise words from Tony, plus a couple of extras below:

Does it have foil in the same way as Celotex? If so and it is to the inside then you are half way there, ok not prefect, but Tony's extra sealing suggestions make it better.

Sarking on top of the rafters? Make sure you have a ventilated gap between the insulation and the sarking. It's meant to be a couple of inches in case any moisture gets through the roof, might be able to get away with an inch.

Shame it was the bathroom, the room with the most water vapour :-/. I'd be happy with sealing the plasterboard tho'.

[basil]

But thats whats recomended for new plaster to allow it to continue drying out so I doubt it has any vapour seal properties.

If ceiling height isn't a problem then adding a layer of foil backed plaster board ( the best kind of vapour seal ) is another solution, plus adds sound insulation. There is no need to remove the boards already up, with all the waste, mess, hours pulling nails out of the rafters etx

[David M]

snip

Adam

If you want to avoid the crap when the time eventually comes to sell, then all of the conversion has to go through building control, who will be especially picky about having adequate insulation. You can check up on the current regs at

J in particular.

the other area that you must take adequate care over is ensuring a 50mm air gap between the insulation and roof, and also adequate roof vents and at the eaves. Insulation manufacturers normally have decent application notes covering this.

cheers

David

[Adam-the-Kiwi]

Yes, it does.

No worries there - there is about 120mm gap between insulation and sarking. Big, deep rafters...

Aye. I was thrilled when I realised that we'd chosen to stuff up the bathroom, of all rooms.

Thanks - Adam...

[Adam-the-Kiwi]

Thanks Tony - that's a relief.

I guess we'll probably use 2 coats of Gyproc drywall sealer topped with a couple of coats of vinyl emulsion, then...

Thanks again - Adam...

[John Rumm]

The usual trick with lofts is some insulation between the rafters, and then some under them before the plasterboard goes on. If you use foil tape over the joins in the final layer then you have a good seal without any additional barrier.