Rising damp
Rising damp is groundwater soaking up through the bottom of a wall. It shows as a band of damp along ground floor walls, often with a tide mark and white salts at the top. It's real, but it's also one of the most misdiagnosed problems in English homes, so it's worth checking the simpler causes first.
Mould and Damp passes your enquiry to one local damp specialist. They find the cause and quote you. We don't carry out treatments ourselves.
Signs to look for
- Damp from the floor up to somewhere under about a metre, on ground floor or basement walls only.
- A wavy tide mark where the damp stops, sometimes with brown staining.
- White, fluffy deposits on the wall: salts left behind as the water dries.
- Plaster that's soft, crumbly or blown, and wallpaper lifting along the bottom.
- Skirting boards that are soft or rotten, and a musty smell near the floor.
Things that look like rising damp but aren't
Before anyone drills a hole, check these. Each one causes damp low on a wall, and each has a cheaper fix:
- Bridged damp course. A path, patio or flower bed built up against the wall above the damp course lets water round it. So can render taken right down to the ground. For new walls, the building regulations guidance puts the damp course at least 150mm above the outside ground (Approved Document C), which is a useful yardstick for older ones too.
- Leaking pipes. A slow leak from a radiator pipe or under a kitchen sink can soak the bottom of a wall.
- Splashback. Rain bouncing off hard ground, or a gutter overflowing onto the bottom of the wall.
- Condensation. The bottom of an outside wall is often the coldest spot in the room, especially behind furniture.
- Blocked air bricks. Under a suspended timber floor, these keep the void dry. Block them and damp builds up.
How it's usually treated
- Fix anything outside that's bridging the existing damp course.
- Where there's no working damp course, inject a chemical one, or less often, insert a physical one.
- Take off plaster that's full of salts, usually up to a metre, and replaster with a salt-resistant mix.
- Let the wall dry out, which takes months in a solid wall, and decorate with a breathable paint in the meantime.
On older solid-walled houses, some specialists prefer to improve drainage and use breathable lime plaster rather than inject. Both approaches have their place; ask why they've chosen theirs.
What it usually costs
| Job | Typical range | Source |
|---|---|---|
| Terraced house | £250–£1,020 | MyJobQuote |
| Semi-detached house | £475–£2,350 | MyJobQuote |
| Detached house | £690–£5,200 | MyJobQuote |
| Injected damp proof course, one wall | £560–£2,200 | MyJobQuote |
| Rising damp, medium-sized property | about £2,000 | Checkatrade |
Sources: MyJobQuote rising damp costs (updated 2 January 2026), which gives an overall range of £250–£6,500; and Checkatrade damp proofing cost guide (last updated June 2026), figures plus VAT.
The biggest variable is replastering. A wall injected but left with salt-laden plaster will keep looking damp, so make sure the quote says clearly whether plaster removal, new plaster and making good are included. Fixing bridged ground levels or blocked air bricks first can make the job much smaller, or unnecessary.
Facts, dates and prices on this page were last checked on 29 October 2026.
Common questions
Is rising damp a myth?
No, but it's diagnosed far more often than it occurs. Water can rise a short way up brick and mortar from the ground. The trouble is that bridged damp courses, leaks and condensation low on cold walls look similar, and they need different fixes.
How high can rising damp go?
Usually not much more than a metre above the floor, and often less. Damp much higher up a wall, or on an upstairs wall, is almost certainly coming from somewhere else.
Can I treat rising damp myself?
DIY injection kits are sold, and lowering a flower bed or clearing an air brick is easy enough to do yourself. Getting the diagnosis right is the hard part. If you're not sure, get it looked at before buying anything.
Why has the plaster gone powdery?
Groundwater carries salts. When it evaporates from the wall, the salts are left in the plaster, where they draw in more moisture from the air and break the surface up. That's why salt-damaged plaster is usually replaced even after the cause is fixed.
Does rising damp affect upstairs flats?
Not directly. It starts at ground level. If you're in an upper-floor flat with damp, look at condensation, leaks from above, and rain penetration first.
Ask for a local damp and mould specialist
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We're a matching service, not the firm that does the work. The specialist contacts you, looks at the problem and quotes you directly. Whether you go ahead is up to you.