DIY Doctor

Can internal dampness be fixed whilst a leak is still active?

Postby Radge70 » Mon Oct 26, 2020 9:33 pm

I have an internal damp problem within my flat that is caused by roofing defects. Unfortunately, the roofing defects won’t be resolved any time soon as there is a 16 way split between all owners and nobody wants to get the work done. I am therefore looking at ways to deal with this internally whilst the leak is ongoing.

I have had a damp specialist in and, he recommended a delta lath cavity wall membrane. When the surveyor was on-site he told me that the good thing about these is that they can be fitted before the source of the leak is stopped, as they create a barrier between the stone wall and the internal plaster wall, meaning the inside will stay dry even as the leak continues to penetrate the stone wall.

There have been a few roofing reports done and it has been established that the source of the leak is rainwater entering the cavity. There are 3 floors on the building, I am the middle floor and the wall is completely saturated (I’ve drilled a hole in it so that I could physically feel this, rather than rely on a damp meter, and there are huge damp stains on the wall as well).

The question I have is whether fitting the membrane would truly do what the damp specialist is suggesting. I think that if the water was running down the outside of the building and making it’s way in that way then this would be plausible. Since it’s coming in through the cavity, I am worried that it may be running down the internal plaster wall directly, thus a barrier attached to the stone wall will do nothing.

Given it could take years to get agreement from the neighbours on the roof fixes (the quotes are massive) I’m in a bit of a fix. I am thinking about opening up the wall to see where the water is running and if it’s down the stone wall then I’m thinking of getting the membrane installed. Is this advisable? If the water is truckling down the internal plaster wall then is there any way of protecting that whilst the leak is on-going?
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Postby stoneyboy » Wed Oct 28, 2020 11:42 pm

Hi radge70
The answer to the question in your title is probably not.
The membrane you refer to will cover the wall but will need plastering and ventilation will be needed top and bottom.
Your best action is to get the roof sorted even if it is done only above your part of the offending wall.
Regards S
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