Guides · Damp guides
Does a new damp-proof course always fix rising damp?
In short: Only if the damp really is rising damp, and only if the other parts of the job are done too: any bridging removed, the salt-contaminated plaster replaced with salt-resistant plaster, and the wall given time to dry. When a new damp-proof course 'fails', the usual reason is that the damp had another cause all along.
When the diagnosis was wrong
The most common reason a new damp-proof course doesn’t cure a damp wall is that the damp was never rising damp. A leaking downpipe, failed pointing, a bridged damp-proof course or condensation will carry on whatever is injected into the wall. That is why we diagnose first: see how to tell if it’s rising damp.
When the wall is still bridged
If soil, a path, a patio or a rendered plinth sits above the new damp-proof course outside, moisture goes around it. Ground levels need to sit comfortably below the damp-proof course, and render should stop above it, or the treatment can’t work.
When the old plaster is left on
Years of rising damp leave salts in the plaster, and those salts draw moisture from the air. If the old plaster stays, the wall stays damp and stained even though the new damp-proof course is working. The contaminated plaster has to be hacked off, typically to around a metre high or further where the damp or salts go higher, and replaced with a salt-resistant plaster system.
When it hasn't had time to dry
A thick solid wall can take several months to dry out after treatment. Decorating with vinyl wallpaper or oil-based paint too early traps the moisture and makes it look as if the treatment has failed. See how long damp proofing takes.
How we do it
We confirm rising damp on a survey first. Where it is confirmed, we inject a new chemical damp-proof course, hack off and replaster with salt-resistant plaster, and make good and decorate ourselves. The damp-proof course is guaranteed for 30 years and the replastering for 10 years. More about rising damp treatment.
Frequently asked questions
Does a new damp-proof course always fix rising damp: FAQs.
Can a damp-proof course be injected without replastering?
It can be injected, but without removing salt-contaminated plaster the wall usually stays damp and stained, so we don't recommend it.
My house already has a damp-proof course. Why is it damp?
It may be bridged, damaged, or the damp may have another cause entirely. A survey will tell you which.
Does the guarantee cover damp from other causes?
No. A rising damp guarantee covers failure of the damp-proof course we installed, not condensation, leaks or later bridging.
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