Damp Proofing London
Damp gets misdiagnosed more than almost any other defect in London homes — and the wrong treatment is expensive and useless. A chemical damp-proof course injected to cure what is actually condensation, or tanking applied over a penetrating leak that was never fixed, solves nothing and the stain comes straight back.
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- Free On-Site Survey
Damp Proofing London
Damp gets misdiagnosed more than almost any other defect in London homes — and the wrong treatment is expensive and useless. A chemical damp-proof course injected to cure what is actually condensation, or tanking applied over a penetrating leak that was never fixed, solves nothing and the stain comes straight back.
There are three distinct problems with three different cures. Rising damp travels up from the ground through a failed or absent damp-proof course and needs a new DPC and replastering. Penetrating damp comes through walls from outside — failed pointing, leaking gutters, cracked render — and is cured at the source. Condensation, by far the most common in flats, is a ventilation and heating problem, not a building fault.
We diagnose before we quote. A proper survey with moisture readings tells us which of the three you actually have, so the treatment matches the cause — whether that is a new DPC, external repairs, tanking a basement, or fixing ventilation.
What's Included
- Full damp survey with moisture readings, inside and out
- Diagnosis distinguishing rising, penetrating and condensation damp
- Injected chemical damp-proof course for genuine rising damp
- External repairs (repointing, render, gutters) for penetrating damp
- Salt-resistant replastering to treated walls
- Cementitious or membrane tanking to basements and cellars
- Ventilation and condensation advice where that is the real cause
- Fixed written quote and guarantee in writing on treated areas
What It Costs in London
These are guide prices to help you budget. We give you a fixed, written quote after a free on-site survey — no call-out charge and no surprises later.
| Work | Guide Price |
|---|---|
| Damp survey & diagnosis (with moisture readings)Survey fee often credited against works | £200 – £500 |
| Rising-damp DPC treatmentTypical whole-property chemical damp-proof course | ~£3,250 |
| Replastering after DPCSalt-resistant replaster to treated walls | £450 – £800 / room |
| Penetrating damp — external repairsRepointing, render or gutter repair at source | from £400 |
| Basement / cellar tankingCementitious or membrane tanking system | from £150 / sqm |
Guide prices only — every job is confirmed with a fixed written quote after a free survey. Prices exclude VAT where applicable; your written quote states the VAT position clearly.
Our Process, Step by Step
Damp survey & diagnosis
We inspect inside and out, take moisture readings, and identify whether you have rising, penetrating or condensation damp — the single most important step, because every cure is different.
Treat the cause
Rising damp gets a new injected DPC; penetrating damp gets the external defect fixed at source; condensation gets ventilation and heating addressed. We treat what is actually wrong, not a guess.
Replaster or tank
After a DPC we hack off contaminated plaster and replaster with a salt-resistant system. For basements and cellars we apply a full tanking system to hold back ground water permanently.
Dry out & decorate
New plaster is left to dry fully — rushing it traps moisture and the stain ghosts back. Once moisture readings confirm it is dry, we mist-coat and decorate, or hand over ready for your decorator.
Frequently Asked Questions
A proper damp survey with moisture readings costs £200–£500, often credited against the works. A typical whole-property rising-damp DPC treatment runs around £3,250, with salt-resistant replastering at £450–£800 per room on top. Penetrating-damp external repairs start from £400, and basement tanking from around £150 per square metre. We quote a fixed price after diagnosis.
Rising damp shows as a tide-mark up to about a metre on ground-floor walls with no obvious external cause. Penetrating damp appears as localised patches that worsen after rain, often linked to failed pointing, gutters or render. Condensation shows as black mould around windows, in corners and behind furniture, worst in winter. A survey with moisture readings confirms which you have — and the cure for each is completely different.
Only if you genuinely have rising damp from a failed or absent damp-proof course. An injected DPC does nothing for penetrating damp or condensation — which are far more common — so injecting one without diagnosis wastes money and leaves the real problem untreated. That is exactly why we survey and diagnose before recommending any treatment.
When a wall has suffered rising damp, hygroscopic salts are drawn into the old plaster and continue to attract moisture even after the DPC is installed. The contaminated plaster has to be hacked off and replaced with a salt-resistant replastering system, or the damp staining returns through the new decoration. Replastering is a necessary part of a lasting rising-damp cure.
Yes. For below-ground rooms suffering water ingress, tanking — a cementitious coating or a cavity-drain membrane system — holds back ground water and creates a usable dry space. We assess the construction and water table and specify the right system, from around £150 per square metre, with a guarantee on the tanked area.
Leak Damage Repair & Reinstatement
One contractor from leak trace to flawless reinstatement — plumber, plasterer and decorator on one team. Specialists in London ceiling leaks and insurance reinstatement work.
View service Cost GuideDamp Proofing Cost in London: Rising Damp Treatment Guide 2026
Damp proofing in London costs from a £200–£500 survey to ~£3,250 for a full rising-damp DPC job. See costs by damp type plus replastering prices here.
Read the guideAcross Every London Borough
We diagnose and treat rising, penetrating and condensation damp in period houses, garden flats and basements across every London borough — from Greenwich and Camden to Wandsworth and Hackney.
Get Your Free Survey & Fixed Written Quote
Book a free on-site survey and we'll return an itemised, fixed-price quote in writing — anywhere in London. No call-out charge, no surprises later.
- Same-day callback
- Fixed price, in writing
- Guaranteed workmanship