The pattern is distinctive: a tide-mark of discolouration on the internal wall that reaches up to around a metre from the floor and no higher, with the skirting board paint bubbling or peeling and the timber sometimes soft to the touch behind it. It's usually worse in winter and in rooms with an external wall on the affected side.
This height-limited pattern is the key diagnostic clue. Moisture rising from ground level or the base of the wall, rather than coming from above through the roof or a leak, produces exactly this shape of staining.
Why the staining stops where it does
Moisture drawn up through masonry from ground level, or moisture crossing the wall near its base, evaporates as it rises, which is why the staining fades out at a fairly consistent height rather than continuing all the way up the wall. That's different from a roof leak or plumbing leak, which tends to show as a stain spreading down from above or around a specific fitting.
The likely causes
- External ground level raised above the internal floor level, or above the damp-proof course, bridging it and letting moisture track straight into the wall
- A blocked or bridged cavity, where debris or an added path or patio has created a route for moisture to cross what should be a clear cavity gap
- A damp-proof course that has failed with age or was bridged by later building work
- Impermeable internal finishes, such as cement-based render or vinyl wallpaper, trapping moisture in the wall that would otherwise evaporate through it
How to check which applies
Compare the external ground level against the internal floor level at the affected wall — a flower bed, patio or driveway raised up over time so that it sits level with or above the damp-proof course is one of the most common and easily overlooked causes. Establish whether the wall is solid or cavity construction, since a bridged cavity is only relevant to cavity walls and points you toward a different repair route entirely.
Check what the internal wall finish actually is — a modern cement-based render or a heavily painted, non-breathable finish on an older solid wall can trap moisture that a traditional lime-based finish would have let evaporate freely, mimicking a damp-proof course failure even where the damp-proof course itself is fine.
Why a damp specialist survey matters here
Diagnosing damp by symptom alone is unreliable — a damp meter reading high at skirting level doesn't by itself tell you whether the cause is rising damp, a bridged cavity, or a finish trapping moisture from a different source such as condensation. A proper damp survey looks at construction type, ground levels, and finishes together before recommending any remedial measure, and that's worth getting before committing to a specific fix.
Common questions
Is damp at skirting level always rising damp?+
No — the height pattern is consistent with rising damp, but a bridged cavity or raised external ground level can produce an identical appearance without the damp-proof course itself having failed. The distinction matters because the repairs are different.
Will just raising the internal heating dry the wall out?+
It might reduce visible dampness slightly, but if the moisture source — a bridged path, raised ground, or failed damp-proof course — isn't addressed, the damp returns as soon as heating patterns change, particularly in winter.
Does this damage anything structural over time?+
It's cosmetic in the early stages, but sustained damp at skirting level rots skirting boards and, if the floor construction is timber, can eventually reach joist ends built into the wall. That's worth addressing before it progresses that far.
Get a proper damp diagnosis, not a guess
We check ground levels, wall construction and finishes together and give you a written assessment before recommending any repair.