Basement damp proofing with a membrane

25 Aug 2011
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United Kingdom
We recently moved into a ground and basement floor flat in a converted London Victorian terrace, which we have bought.

The basement level has two main rooms, both bedrooms, a small hallway and a shower room bathroom. Both bedrooms have windows onto deep lightwells going down to them, with the outside ground level at ceiling height. This is where the front and back walls of the house are. The side walls of the basement area, are presumably just against earth, as neither house either side has a basement visible from above ground (we haven't asked them if they have cellars).

We had a homebuyers survey done before we moved in and were told of high damp readings being registered at the base of the walls to the front and rear (both bedrooms) a high damp reading was also registered in one patch near the middle of the floor.

Previously there had been a damp proof course applied to the front and read walls by a damp proofer as the previous owners had noted damp.

We got damp specialists round as advised. They told us that they thought that there had been a transference of moisture from the walls to the edges wooden flooring when the old damp problem had occurred and that this was causing the high damp readings there. They got no damp reading in the middle of the floor and said there was no other evidence of a problem with the floor membrane and that we should get the floorboards cut away slightly and a membrane fitted behind new skirting boards which should fix the problem.

And so we bought the flat.

When it came for the work to be done to the floor, the guy came round took off the skirting and said it was sodden underneath and there was no evidence of a floor membrane.

To cut a long story short, same damp people came back round, said floor has high damp readings, they think a new membrane needs fitting, all flooring up, internal walls and bathroom removing, all floor taken up, new screed put down with a damp proof treatment. Cost quoted £16k plus VAT.

However, they have not drilled into the floor or anything to take damp measurements, just tested round the sides

Looking into this someone suggested we could instead use a Delta membrane, saving time and money and intrusiveness. Read some interesting stuff on here about this method, but wondered if anyone who knows can help answer my questions.

1) There is no evidence of damp beyond these high readings at the edges and one patch on each bedroom floor which someone suggested maybe where a radiator pipe is and the walls are all fine - do we just do a floor membrane or should the walls be done too.

2) If we have to do the walls, would we therefore have to do all the internal stud partition walls too

3) Will we need a pump, there are drains in each of the lightwells

4) What do we do about the wooden staircase that goes down to the basement

5) Any thoughts on what this sort of hing costs. Area is about 40m2, two bedrooms are 4x5ish each,plus hallway and small bathroom.

I'd really appreciate any advice. Thanks
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