Lobster wrote:
The Natural Philosopher wrote:
RatRibs73 wrote:

anything else. You wedge it between timber studwork, and use aluminium
tape over it all to create a water and draught proof seal.

I didn't know that (the Al tape bit) - makes sense, and glad I found
out as I'm doing exactly this job at the moment (qv my recent query on
drylining a kitchen).

Ply membrane is a typo. damp proof membrane - usually polythene.

Heh, I was scratching my head over the ply membrane! But do you really
need the DPM anyway if you have a clear air gap between the studwork
and the wall? (And the insulation is foil-backed?)

David

No, but belt and braces, and you have to fix the studs to
something..typically what you want is surface finish, then vapour
barrier (the aluminium tape, and the celotex facing) then studs and
celotex matrix for insulation. At this point you get cold and
condensation make take place in the gap..so you want to try and both
keep the studs clear of damp wall, and also allow perhaps moisture to
permeate outwards through the wall - or provide ventilation (airbrick etc)

Its a fine point. If the celotex and al tape is good, then no internal
moisture will penetrate, and the only damp will come in from the
outside, and can leave the same way. Then a poly membrane will keep it
away from the cavity.

OTOH if you HAVE got moisture from the room seeping in, then the last
thing you want is to trap it in the wall..