DIY Doctor

Damp Proof Company wants £1700 but I think I can do it myself (with a bit of advice!)!)

Postby Radge70 » Wed Nov 11, 2020 1:20 pm

I have had some work recommended by a national damp proofing company at a cost of over £1700 (for a 3m x 2.4m wall).

The report recommends the following:
• Remove wall plaster to the external wall full height
• Fit delta lath cavity wall membrane
• Dot Dab plasterboard to membrane with skim coat plaster finish

So having read up on this, I think it will be possible to do it myself using a “PermaSEAL 3 Damp Proof membrane kit“ at £105. The plasterboard I am thinking of using is “Knauf Vapour Panel Square Edge - 12.5mm X 1.2m X 2.4m”, which would cost £45 for 3 sheets

I’ve not opened the wall up yet but I’m planning to make a 20cm x 20cm hole to see what’s behind the plaster. I think, however, that it is the stone wall, then the cavity space then lath and plaster.

So to do this myself (as an absolute rookie and with the help of a handy friend) the bit that I’m having trouble understanding is as follows:

Correct me if I am wrong but my understanding is that the cavity wall membrane should be attached to the bare stone wall (on the inside).
I then (according to to the damp company) Dot Dab the plasterboard to the membrane, which is the bit that’s puzzling me……

I thought that a cavity was quite a large gap between the stone wall and the interior wall. If the membrane goes directly on the stone wall and then the plasterboard is dot dabbed to the membrane then surely this gap would no longer exist (which I think it’s meant to)? Further, I’m struggling to work out (even with a final skim coat) how this membrane/plasterboard combo will protrude far enough from the stone wall so that it’s flush with the adjoining walls.

Would it be equally good to fit the membrane to the stone wall and then make a frame for the plaster to be nailed to? E.g. the success of the damp proofing job isn’t dependant on the plasterboard being stuck to the membrane?

I’m actually also looking to avoid the need for a skim coat as well as I think I could just line the plasterboard and paint it.
Radge70
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Postby stoneyboy » Sat Nov 14, 2020 5:49 pm

Hi radge70
You are not really giving us enough information for us to advise.
Suggest you open up as per your post then post pictures of what you have found.
Regards S
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