Damp proofing covers a wider spread of jobs, and a wider spread of prices, than almost anything else in this series. In 2026, chemical damp-proof course (DPC) injection — the standard treatment where a wall's original damp course has genuinely failed or is absent — typically costs £600–£2,500 on an ordinary semi-detached house, worked out at roughly £60–£160 per linear metre of wall treated. Retrofitting a physical damp-proof membrane instead of an injected chemical runs to £2,500–£7,500, and tanking a basement or cellar is a bigger job again, at £4,000–£14,000 or more. Every one of those figures assumes the diagnosis behind them is correct.
What actually moves the number, more than house size, is which of these jobs you need — and whether you need one at all. Wall length, method, and how much replastering and making good follows the injection all matter. But in this particular corner of the trade, getting the diagnosis right matters more than any of them, because a wrongly-diagnosed job is money spent on a problem you don't have while the real one carries on unfixed.
I don't inject anything into walls for a living — I diagnose, contractors treat — so this is a straight read on 2026 pricing from someone who gets called in, more often than you'd think, after a chemical DPC has already gone into a wall that had condensation, not rising damp. Most "rising damp" I'm asked to look at is exactly that, and no chemical injected into brickwork will fix a ventilation problem.
The short answer
Figures below were checked on 27 July 2026 against Checkatrade, MyJobQuote and HomeOwners Alliance cost guides, cross-referenced against several UK damp-proofing specialists' own published price lists. As with most trades in this series, the South East and London sit toward the top of these ranges, and a rendered or clad wall costs more to treat than exposed brick, because the covering has to come off before injection and go back on afterwards.
| Job | Typical cost (2026) | What's included |
|---|---|---|
| Independent damp survey | £150–£300 | Diagnosis before any treatment — up to £600 for a larger or more thorough job |
| Chemical DPC injection, small terrace | £600–£1,200 | Injected chemical cream along the affected wall run |
| Chemical DPC injection, 3-bed semi | £1,000–£2,500 | Full external wall run; the most common job in this category |
| Damp-proof membrane retrofit | £2,500–£7,500 | Physical membrane, often used where injection isn't suitable |
| Basement or cellar tanking | £4,000–£14,000+ | Full waterproof tanking system across a larger below-ground area |
Per linear metre, chemical injection itself typically runs £60–£120, with premium quotes reaching £160–£195 once replastering the injection holes is included. On a straightforward 4-metre run of solid wall in a 3-bed semi, that puts the injection element alone at roughly £250–£650, before making good — which is one reason two quotes for what sounds like the same job can look wildly different: one is injection only, the other bundles in replastering, skirting and redecoration.
What drives the price
Wall length, not house size. You're paying for linear metres of wall treated, not square footage of house. A small terrace with a long run of affected wall can cost more to put right than a larger detached house with a short one.
Method. Chemical injection is the cheapest and by far the most common approach, and the one most quotes default to. Electro-osmotic and magnetic-field systems, which use an electrical charge or wiring rather than a chemical barrier, cost more per metre — roughly £75–£140/m for electro-osmotic and around £125/m for magnetic field — and tend to get specified for older solid-wall or listed properties where a chemical injection risks doing more harm than good to the wall's ability to manage moisture.
Making good. Replastering the affected wall to about a metre up — roughly the height rising damp actually reaches — new skirting, and redecoration are usually priced separately from the injection itself, at £100–£500 for a modest single wall, more if flooring or a larger area is affected.
Access. Render, external cladding or a solid floor abutting the treated wall all add cost, because they need removing before injection and reinstating afterwards.
Region. Kent, Sussex, Surrey and London trend above the national figures quoted here, in line with most trades in this series.
Do you actually need it?
This is the section that matters more than any of the numbers above. Several UK damp specialists publish figures suggesting most properties called out for suspected rising damp don't actually have it — condensation, a blocked or leaking gutter, a bridged cavity, or failed pointing account for most of what ends up labelled "rising damp" on a quote. That's a trade estimate rather than a peer-reviewed statistic, but it lines up with a genuine, long-running argument inside the surveying profession itself.
In 2009, Stephen Boniface, then chair of the RICS Building Surveying Faculty, told the institute's members that "true rising damp" is a myth and that chemically injected damp-proof courses are "a complete waste of money" in most of the cases they're sold for — a claim he later softened, putting the misdiagnosis rate at the "vast majority" rather than all cases. RICS's own response was to start putting "rising damp" in inverted commas in its member guidance.
More recently, and more authoritatively, RICS, Historic England and the Property Care Association jointly published a position statement in September 2022 on investigating moisture in traditional buildings. Its central point is that older, solid-walled buildings shouldn't be judged against modern damp-proofing assumptions, that damp is usually multi-factorial, and that a proper diagnosis means dealing with obvious external defects first and monitoring the result before reaching for a chemical solution — not a five-minute reading taken with a moisture meter held against the plaster.
The tell is usually the pattern, not a single number. Genuine rising damp is confined to roughly the bottom metre of a wall, tracking the height groundwater can wick up through brick or stone by capillary action, and it tends to leave a tide-mark and salt staining. Condensation shows up as black mould in corners, on cold external walls and around window reveals — wherever air can't circulate — and no chemical DPC touches it, because the moisture isn't coming from the ground at all. A handheld moisture meter (I've written about where these lie) can register a false-high reading from salts or surface condensation just as easily as from a real capillary problem, which is exactly how so many chemical DPCs end up sold on the strength of one number rather than a proper diagnosis.
There's also no dedicated grant for damp proofing in 2026. ECO4 funds it only incidentally, where damp or ventilation work is genuinely needed to hit an EPC improvement target alongside insulation measures — it isn't available as a standalone grant, whatever a sales quote might imply.
What I'd watch for in a quote
- Who's doing the surveying. A "free damp survey" from the same firm that then quotes you the treatment is a conflict of interest, not a bargain. Get an independent assessment from someone with nothing to sell you first.
- PCA membership and an insurance-backed guarantee. Property Care Association membership and a guarantee that survives the firm folding matter more than a cheaper headline price.
- External causes ruled out first. Gutters, ground levels, render, pointing and bridged cavities should all be checked and excluded before a chemical injection is proposed, per the RICS/Historic England/PCA approach above.
- Per-metre pricing broken down on the written quote, not a single lump figure, so you can see what you're actually paying for and compare quotes properly.
- No pressure to sign on the day. A legitimate specialist doesn't need a same-visit signature; if that's the pitch, get a second opinion before you commit.
Questions I get asked
How much does damp proofing cost? In 2026, chemical DPC injection typically costs £600–£1,200 for a small terrace and £1,000–£2,500 for a 3-bed semi, at roughly £60–£160 per linear metre. A damp-proof membrane retrofit runs £2,500–£7,500, and basement tanking £4,000–£14,000 or more. Replastering afterwards is usually priced separately, at £100–£500 for a modest single wall.
Do I actually need a damp-proof course, or is it condensation? Often it's condensation. Genuine rising damp sits within roughly the bottom metre of a wall with a tide-mark and salt staining; condensation shows up as black mould in corners and on cold surfaces, and no chemical DPC touches it. If external causes haven't been ruled out before an injection is proposed, get a second opinion before anyone drills a hole in the wall.
Is chemical DPC injection guaranteed to fix rising damp? Only if the diagnosis is right. A reputable, PCA-member specialist will guarantee the injection process itself, usually with an insurance-backed guarantee that survives if the firm closes. No guarantee covers a wrong diagnosis — if the real cause is penetrating damp or condensation, injecting a chemical DPC does nothing for it.
How much does it cost to sort out damp before selling a house? It depends entirely on what type of damp it turns out to be, which is why I'd get it diagnosed before pricing a fix. A condensation problem might need little more than better ventilation; genuine rising damp could mean £1,000–£2,500 for injection plus making good. Either way, putting the condition on the table before marketing, through a seller's survey, tends to work out cheaper than a buyer's survey finding it mid-sale.
If a survey or a quote has flagged damp and you'd like an independent read on what type it actually is before anyone drills a hole in the wall, that's exactly what my building survey work is for — and if you're selling, a Home Insight Survey puts the same answer on the table before a buyer's surveyor finds it for you. Call 07946 618203 or get in touch and I'll give you a straight answer before you spend the money.
Small print. This guide is general information, not advice on a specific property, and it doesn’t replace a proper survey and quote for your own home. Prices were researched and correct to the best of my knowledge on 27 July 2026; costs move and vary by region and property. Always get at least three written quotes, and get an independent diagnosis before agreeing to any chemical DPC work.