Rising damp is the most argued-about defect in British housing: genuinely destructive when real, yet diagnosed far more often than it occurs — usually by companies selling the cure. This guide covers what actually causes it, what it looks like, and how to fix it without paying for treatment you do not need.
What Causes Rising Damp?
Rising damp is groundwater climbing up masonry by capillary action. Most walls built after the 1870s include a damp-proof course (DPC) — slate, bitumen or plastic — that blocks this. True rising damp therefore needs a failed or absent DPC, or something bridging it: raised flowerbeds or paths against the wall, render lapped over the DPC, debris in the cavity, or internal floor levels above the DPC line. In practice, ‘bridging’ explains more cases than DPC failure.
What Does Rising Damp Look Like?
The signature is a tide mark: a horizontal band of staining or salt residue, typically stopping within a metre of floor level, with peeling paint or blown plaster below it and dry wall above. Damp that appears at high level, in corners, around windows or after rain is almost certainly condensation or penetrating damp instead — different causes, different fixes, and no injection cream required.
How to Fix Rising Damp
Fix the cause first: lower external ground levels, clear bridged renders, unblock subfloor ventilation. Where the DPC has genuinely failed, remedial options include injected chemical DPCs and, in severe cases, physical replacement — followed by salt-contaminated plaster renewal. But the ordering matters: treatment without diagnosis is how homeowners pay twice.
Get an Independent Verdict First
An independent damp survey from an RICS surveyor — with no treatment to sell — tells you which type of damp you actually have. See also our guides to damp patches on internal walls and damp survey costs.
Tide marks or stubborn low-level damp? Call 020 4579 8270 for an independent damp survey in Manchester and the North West.