Damp proofing and penetrating damp treatment in London
Penetrating damp comes in horizontally, through a specific defect: a cracked render, a blocked gutter overflowing down a wall, a perished pointing joint, ground built up above the damp-proof course. Treating it means finding and fixing that defect, not just applying a waterproof coating to the inside of the wall and hoping.
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What this includes
- Tracing and fixing the external entry point
- Damp-proof course installation and repair
- Repointing, render repair and defect remediation
- Internal replastering with the correct system, post-fix
- Ground level and drainage corrections against a wall
- Guttering and downpipe faults that feed penetrating damp
Worth knowing first
Some of this may save you a callout entirely. We would rather tell you than not.
A waterproof coating without fixing the cause just moves the problem
Tanking or a waterproof paint on the inside of a wall stops the symptom showing, but the water is still getting in — it tends to travel sideways instead and shows up somewhere new. Fix the external defect first.
Guttering is the single most common cause
A blocked or leaking gutter running water down an external wall for months produces exactly the pattern people call rising damp. Checking the guttering above the affected wall costs nothing and rules out the commonest cause.
Ground level matters more than people expect
A path, patio or flower bed built up against a wall above the damp-proof course bridges it, letting ground moisture straight into the brickwork above. Lowering the ground level is sometimes the actual fix, not anything done to the wall itself.
Replastering needs the right system, and needs the wall to dry first
Replastering over a wall that has not been allowed to dry out, or with an ordinary plaster rather than a breathable or salt-retardant system where needed, brings the problem back. This is agreed as part of the job, not left to whoever tiles or decorates afterwards.
Common questions
How is penetrating damp different from rising damp?
Penetrating damp comes in horizontally through a specific defect and can appear at any height. Rising damp travels up from the ground through the wall itself and is limited to roughly the height groundwater can wick to — usually under a metre.
Will the patch on my wall go away once the cause is fixed?
The wall needs time to dry out afterwards, which can take weeks depending on the wall’s thickness and how long it was wet. Redecorating too soon traps the remaining moisture behind the new finish.
Do you install damp-proof courses?
Yes, both new installation and repair of an existing one that has failed or been bridged.
Can this wait, or does it get worse?
Left alone, penetrating damp typically gets worse — timber can be affected, and the area of wall involved grows. It is worth dealing with once identified rather than monitoring it.
If it turns out to be plumbing
Where the cause is a leak or a pipe rather than damp itself, these are the pages that cover it.
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General Plumbing
Taps, toilets, radiators and pipework. The jobs that never quite get done.
More on General Plumbing -
Leak Detection
Hidden leaks traced with acoustic and thermal equipment, before floors come up.
More on Leak Detection
Damp and condensation, the other pages
Related advice
Need damp proofing & penetrating damp in London?
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