On Jul 21, 6:22*pm, "js.b1" wrote:
Walsh did...
Bitumen on wall, then p/t battens, rockwool between battens, celotex
over battens, foil tape over joints, PB over celotex, taped joints.

If you do not bitumen a single leaf wall you will get chronic water
ingress.
If you do not tape the joints of the celotex or tape PB, you do not
have a vapour barrier.

So basically he was relying on 2 vapour barriers.
Fine as long as that in the middles does not fail - and there comes an
issue re "drylined socket accessories" in something like a kitchen.
The moisture can get in, can't get out of the PB, can't get out of the
wall. One reason why I always insulated behind backboxes to remove the
cold bridge which worked superbly on a test kitchen (just 6mm Marmox
is enough, but I used 12.5mm since I had bits kicking about).

In the middle go p/t battens - and hopefully stainless screws where it
is single leaf brickwork.

The only foolproof way would be to turn it into a "pool shower room".
Seal with wall with Primer-G / Primer -S / SBR, then Mapei Keraflex,
then Marmox in 6-50mm thickness, then polyurethane sealant & tape the
joints, then plaster skim with tiles or whatever on top. The problem
is that gives too low a U value for most applications, it is however
very waterproof. Stick a piece of Marmox behind any backboxes, since
it is extruded polystyrene it is tough enough to work ok.

There is no perfect solution, I too do not like even p/t battens in
any wall which gets damp and much prefer bonding the insulation to the
wall. In that respect I am surprised there is not a "Marmox-PIR" (ok,
there is, but rarely found) in terms of a cement & glass-fibre backed
PIR which can be bonded directly to the wall with Keraflex. That
ensures nothing is getting through your single brick skin (or double
solid brick which can be just as bad in certain circumstances).


Ah, that makes more sense I only saw as far as the bitumen coating
and cutting a doorway out.


NT