What is rising damp?
Rising damp is groundwater drawn upwards through the pores of brick, stone and mortar by capillary action. It only occurs where a property has no effective damp-proof course (DPC), or where an existing DPC has been bridged, breached or has failed. Because the rise is limited by evaporation from the wall face, it affects ground-floor walls only and usually stops below about one metre.
That physical limit matters: damp above head height, damp on an upper floor, or damp on an internal partition away from the ground is not rising damp, whatever a free "damp inspection" from a remedial contractor may say.
The signs of rising damp
A horizontal tide mark below one metre
Genuine rising damp stops where evaporation balances capillary rise — usually 600mm to 1.2m above floor level. A tide mark that runs at a consistent height along a ground-floor wall is the single most recognisable indicator.
Salt banding and crystal deposits
Groundwater carries hygroscopic nitrate and chloride salts into the plaster. A fluffy white bloom, or plaster that stays damp in humid weather, points to salt contamination — confirmed by salt analysis, not a meter alone.
Blown plaster and decaying skirtings
Hollow-sounding plaster, lifting wallpaper, flaking paint at low level and soft or crumbling skirting boards indicate prolonged moisture in the wall base rather than a surface condensation problem.
Ground level above the damp-proof course
Raised paths, patios, render carried down over the DPC, or a rendered plinth bridging the course allow moisture to pass the barrier. This mimics rising damp exactly and is often correctable without injection.
Unsure which type of damp you have? Compare the patterns in our signs of damp guide.
What causes rising damp — and what each fix involves
| Cause | What is happening | Correct remedy |
|---|---|---|
| No damp-proof course | Common in solid-wall properties built before roughly 1875. There is no barrier at all, so moisture rises freely through the masonry. | Chemical DPC injection or an alternative barrier, followed by salt-retardant replastering. |
| Bridged damp-proof course | External ground, render, debris in the cavity, or an abutting flowerbed carries moisture over an otherwise sound DPC. | Lower ground levels, cut back render, clear the cavity. Usually a fraction of the cost of injection. |
| Failed or breached DPC | Older slate or bitumen courses can crack through settlement, or be cut through by later works such as extensions and service entries. | Localised repair or re-treatment of the affected section only. |
| Misdiagnosis (condensation or a leak) | The most frequent finding. Low-level damp with black mould, or damp beneath a kitchen or bathroom, is rarely rising damp. | Ventilation improvement or leak repair — no damp-proofing required. |
How rising damp is properly diagnosed
- Calibrated moisture meter readings taken in a profile up the wall, not single spot readings
- Deep-wall measurement to distinguish surface moisture from moisture within the masonry
- Salt analysis for nitrates and chlorides, the signature of groundwater rather than condensation
- External inspection of ground levels, DPC line, render, pointing, gutters and downpipes
- Thermal imaging to separate cold-surface condensation and hidden leaks from true rising damp
- Timber inspection at skirtings and joist ends for wet rot, dry rot and woodworm activity
We never sell remedial works, so there is no incentive to recommend a chemical DPC you do not need. If your damp turns out to be a blocked gutter or a bridged course, that is exactly what the report says.
Rising damp treatment costs in the UK
| Work | Typical UK cost |
|---|---|
| Independent rising damp survey and report | £180 – £350 |
| Chemical DPC injection (per linear metre) | £70 – £120 |
| Single affected wall, injected and replastered | £700 – £2,000 |
| Full ground floor treatment | £2,500 – £5,000+ |
| Lowering external ground levels / removing bridging | £200 – £900 |
Full pricing is broken down in our damp survey cost guide, and lender requirements are covered in our damp and timber survey page.
Get an independent rising damp survey
CSRT accredited, LM3DMC qualified, 18 years' experience, UK-wide coverage and fixed fees. Reports are accepted by mortgage lenders, private landlords and social housing providers.
Looking for a surveyor in your town? See our damp surveys near me page or browse all locations we cover.
Rising damp FAQs
How high does rising damp go?
Typically 600mm to 1.2m above floor level. Damp higher than that on a ground-floor wall usually has another cause, such as penetrating damp or condensation.
Can rising damp be fixed permanently?
Yes — provided the true cause is addressed. A correctly installed DPC, or removal of bridging, with salt-retardant replastering where required, resolves it long term.
Will rising damp stop a mortgage?
Not automatically. Lenders usually retain funds until a specialist damp and timber report sets out the cause and the cost of remedy. We produce lender-accepted reports for exactly this purpose.
Is a damp meter reading enough proof?
No. Electrical resistance meters read salts and surface moisture too. A defensible diagnosis needs a reading profile, deep-wall measurement and salt analysis alongside external inspection.