Damp Proofing Question

Worth getting dpc for 19th century granite cornish cottage?


We moved into a 1860c. granite Cornish Cottage in April and it suffers badly from damp coming through the walls from the outside, causing all the plaster to blow and paint to peel etc. We were aware damp was likely to exist in some form in the house when we bought it, but not quite to the extent it is actually at!

We had a damp proof company come and have a look today and they gave us a quote of £4000 for two weeks work. This would include;

taking back the old plaster and render
applying dpc by drilling into the walls and inserting chemicals
putting on another layer of 'stuff' (my wifes description, I was at work when he came round)
3 layers of tanking
re plastering

What I wanted to ask was

Having done some research into damp in older houses, most books and websites have said that a dpc was counter-productive in actually combating damp as it trapped it rather than solved the problem. So is it worth getting the dpc?

When the builder had a look, it was almost entirely visually (it is pretty obvious the damp) but he did measure the water content in the walls, using a 'two pronged device' according to my wife. For an initial examination, is this normal?

Secondly is £4000 a reasonable amount? it is the first quote we have had, and we will of course be getting a couple more, but i have no real knowledge of what the price should be.

Many thanks for any advice or direction on this issue.



2 Answers

Best Answer

Injected dpc's in older building are something to be cautious of as they are not always effective and can divert the problem elsewhere. Also why is there a recommendation for tanking - does the house have a basement or built into a hill or something?

You would be better trying to resolve the root cause - namely is the damp a result of leaking gutters, downpipes or drainage pipe? Is the outside ground levels to high up against the outside of the building? If the building is rendered, is this a cement render and is it cracked or damaged, thus allowing water to penetrate through but not allowing for natural evaporation? Is the building well ventilated? etc etc. I would answer these questions before spending £4000 and definitely get a 2nd quote and more importantly a 2nd opinion.

Hope this helps.

Answered 17th Oct 2013

Brayfield Construction

Member since 1 Oct 2013

Would definitely be getting a second opinion, the damp proof company is only trying to cover up the problem rather than solve it.
Would be looking at the outside of the house to see what has changed and why it is allowing water ingress into the house, what's stopping the house from breathing, have the walls been repointed in the wrong material, are there any leaking gutters or downpipes, is the ground level too high, has it been rendered with a cement based render?
The problem with older houses are they require original materials to allow them to breathe, older materials and new materials do not work very well together.
Injected damp proof courses seldom work in this type of building,
just been up visiting one of my regular customers in a grade 11 listed building where someone has installed a damp proof course and tanking on an internal wall when the problem was water ingress through the roof, they're now having to hack of the plaster and render to allow the wall to dry out properly. A lot of extra work caused by some damp proofing company that's only interested in your money rather than fixing the problem. See this sort of work all the time in older buildings, problems created rather than solved, rising damp is misdiagnosed in over 70% of cases.
You really need someone that understands older houses and how all the materials work together to prevent dampness.
Good luck Alex

Answered 18th Oct 2013

ADR Property Maintenance

Member since 1 Mar 2009

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