Damp Proofing Cost 2026: Rising Damp Treatment Prices UK
Damp proofing a wall with a chemical injection damp proof course typically costs £60 to £200 per metre, averaging around £100 per metre, according to Checkatrade's 2026 cost guide. A typical injection job comes to £1,000 to £3,000, and treating the ground floor walls of a semi detached house averages about £2,000. Tanking a cellar or basement costs roughly £100 to £200 per square metre, with an average near £125.
Before you spend a penny on any of that, make sure you have the right diagnosis. A lot of damp in British homes is not rising damp at all. It is condensation or water getting in from outside, and injecting a chemical into the wall will not fix either. This guide explains the three main types of damp, what each treatment costs and how to avoid paying for the wrong one.
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Types Of Damp
There are three main kinds of damp in houses. They have different causes and very different fixes.
| Type | What causes it | Typical signs | Usual fix |
|---|---|---|---|
| Rising damp | Ground moisture drawn up through masonry where there is no working damp proof course | A tide mark up to about a metre above floor level, salts, crumbling plaster, rotting skirting | Repair or install a damp proof course, replaster with suitable materials |
| Penetrating damp | Rain getting through the walls or roof from a defect | Patches that grow after rain, often higher up the wall or near windows | Fix the defect: gutters, pointing, render, roof, sills |
| Condensation | Moist indoor air meeting cold surfaces | Black mould in corners and behind furniture, wet windows, worse in winter | Better ventilation, heating and insulation |
Rising damp
Most houses built since the late 19th century have a physical damp proof course, a layer of slate, bitumen or plastic in the wall just above ground level. Rising damp happens when that layer is missing, has failed or has been bridged, for example by a flower bed, a raised patio or render that runs down to the ground. Before paying for a new damp proof course, check that nothing is bridging the old one. Lowering a soil level outside can sometimes solve the problem for nothing.
White, fluffy deposits on the wall are often salts left as moisture evaporates. Our guide on how to stop salt coming out of a wall covers what they are and how to deal with them.
Penetrating damp
This is water coming in from outside. Common culprits include blocked or leaking gutters and downpipes, failed pointing, cracked render, defective flashing around chimneys and window sills without drips. Penetrating damp is fixed by repairing the outside of the building, not by treating the inside wall.
Condensation
Condensation is by far the most common damp problem in UK homes. Cooking, showers, drying clothes and even breathing put moisture into the air, which condenses on cold walls and windows. It encourages black mould. The answer is to reduce moisture, ventilate and keep surfaces warmer. Damp proofing treatments do nothing for condensation. If you see it in the roof space, see our guide on loft condensation.
Damp Proofing Prices
The table below draws together the main published price figures for 2026.
| Treatment | Typical cost | Notes |
|---|---|---|
| Chemical injection damp proof course | £60 to £200 per metre, average about £100 | Cream or fluid injected into a mortar course |
| Typical injection job | £1,000 to £3,000 | Depends on wall length and replastering |
| Ground floor walls of a semi detached house | about £2,000 on average | Injection treatment |
| Cellar or basement tanking | £100 to £200 per m2, average about £125 | Cementitious or membrane systems |
| Replastering, drying out and decoration | Usually extra | Often a large part of the total |
Most of a damp proofing bill is not the injection itself. Hacking off old plaster, letting the wall dry, replastering with a salt resistant mix and redecorating can cost as much as the treatment. Ask for each step to be priced separately. It also helps to know how much of the wall will be replastered, what plaster will be used, how long the wall needs to dry and who is responsible for the decoration afterwards, because these details are where quotes differ most.
Injection damp proof course
A line of holes is drilled into a mortar course just above ground level, typically every 100 to 120 mm, and a silicone based cream is injected. It spreads into the masonry and forms a water repellent barrier. Contaminated plaster is usually removed to about a metre high and the wall replastered.
Physical damp proof course
In some walls, especially where the original slate has cracked, a physical course can be inserted by cutting out a mortar joint in sections and inserting a membrane. It is more disruptive and more expensive than injection, and less commonly offered.
Tanking and membranes
Below ground rooms such as cellars cannot have a damp proof course in the usual sense, because the whole wall is in contact with wet ground. Instead, the room is waterproofed from the inside.
- Cementitious tanking is a waterproof slurry or render applied to the walls and sometimes the floor.
- Cavity drain membranes are dimpled plastic sheets fixed to the walls. Water runs down behind them to a drainage channel and a sump pump. They are often preferred for habitable basements.
Remedial plastering
Salts carried up by rising damp stay in the plaster even after the damp is cured. They attract moisture from the air and keep the wall looking damp. That is why replastering is a key part of the job. Specialist renovating plasters or sand and cement with additives are often used. Our plastering guide covers general plastering costs.
Damp Surveys
A good survey is the most valuable money you will spend on damp. It should identify the type of damp and the cause, not just measure moisture.
- Independent surveyors. Some chartered building surveyors specialise in damp and charge a fee for a report without selling you a treatment. This avoids any conflict of interest.
- Specialist damp firms. Many offer free or cheap surveys, then quote for their own treatments. Some are excellent; others sell injection treatments for problems that are really condensation.
- Property Care Association. Members of this trade body work to a code of practice, and some staff hold a Certificated Surveyor in Remedial Treatment (CSRT) qualification.
Be cautious of a diagnosis based only on a handheld moisture meter. These meters are designed for timber and can give high readings on walls with salts, foil backed wallpaper or even certain paints. A proper survey looks at the pattern of damp, the outside of the building, floor levels and ventilation.
DIY vs Professional
Some damp problems are within reach of a confident DIYer. Others need a specialist.
| Job | DIY? | Notes |
|---|---|---|
| Clearing gutters and downpipes | Yes, with safe access | Often fixes penetrating damp |
| Lowering soil or removing debris against walls | Yes | Can stop bridging of the damp proof course |
| Improving ventilation | Yes | Extractor fans, trickle vents, opening windows |
| Repointing small areas | Possible | Use the right mortar; lime for older walls |
| Injecting a damp proof course | Possible with hire kits | Results depend on correct diagnosis and preparation |
| Tanking a cellar | Not recommended | Specialist systems and guarantees |
| Major render or roof repairs | No | Safety and access issues |
Even if you do the work yourself, a professional diagnosis first can save you from fixing the wrong thing.
Guarantees
Many damp proofing firms offer long guarantees, often 20 or 30 years. Check:
- Is it backed by insurance if the company goes out of business?
- What does it cover? Often only the treated section of wall, not new damp from other causes.
- Is it transferable when you sell?
- What conditions apply, for example keeping gutters clear?
How To Keep Costs Down
- Fix the cause first. Gutters, downpipes and pointing are cheaper than wall treatments.
- Get an independent opinion. If you are quoted thousands for injection, a surveyor's report can be good value.
- Check for bridging. Raised flower beds and paths are a common, cheap fix.
- Tackle condensation. Heating, ventilation and a dehumidifier cost little next to building work.
- Get itemised quotes. Compare treatment, replastering and decoration separately.
Fixing Condensation Without Building Work
Because condensation is so common, it is worth ruling it out properly before paying for anything else. These steps cost little and often solve what looks like a serious damp problem.
- Extract at the source. Use the cooker hood when cooking and the bathroom fan during and after showers. A fan that hums but does not pull air is not doing its job; our guide on a bathroom extractor fan not working explains how to check it.
- Dry washing outside or in a vented dryer. A load of wet washing releases a surprising amount of water into a room as it dries.
- Keep a low, steady background heat. Cold rooms that are heated briefly suffer most, because walls stay cold.
- Open trickle vents. Modern windows usually have them for a reason.
- Leave a gap behind furniture. Wardrobes pushed against cold outside walls are a classic spot for mould.
- Run a dehumidifier. Watching how much water it collects in a day is an eye opener and a useful test.
If damp patches shrink after a few weeks of this, the problem was condensation, not rising damp.
Warning Signs Of A Bad Damp Quote
Most damp specialists are honest, but this is an area where homeowners are often oversold. Be wary if:
- the diagnosis is based only on a moisture meter reading with no inspection outside;
- you are told the only answer is injection, with no mention of gutters, ground levels or ventilation;
- damp high up a wall or around a window is described as rising damp;
- there is pressure to sign the same day or a discount that expires tonight;
- the guarantee is not backed by insurance;
- the quote does not explain what plaster will be used afterwards.
A good specialist will be happy for you to get a second opinion.
Damp And Older Houses
Solid walled houses built before about 1920 were designed to breathe. They let moisture in and out through lime mortar and lime plaster. Covering them in cement render, gypsum plaster or impermeable paint can trap moisture and cause the very problem it was meant to solve. Many conservation specialists argue that older homes are better treated by removing impermeable materials and using lime, rather than injecting chemicals. If you own a period home, look for a surveyor with experience of traditional buildings.
How Long Does Damp Proofing Take?
An injection treatment on the ground floor of a typical house is often a two or three day job, plus time for the walls to dry before replastering and decorating. Drying times vary widely; a rough rule often quoted is a month for every 25 mm of wall thickness, so do not rush to paint.
FAQs
How much does it cost to damp proof one wall?
At £60 to £200 per metre, a 4 metre wall would cost roughly £240 to £800 for the injection, plus replastering and decorating.
Does house insurance cover damp?
Usually not, because damp tends to develop gradually. A sudden event, such as a burst pipe, may be covered.
Is rising damp a myth?
No, but it is less common than many people think, and it is often misdiagnosed. Condensation and penetrating damp are more frequent causes of damp walls.
Can I sell a house with damp?
Yes, but a buyer's survey will usually flag it and may lead to price negotiations. Fixing the cause and keeping paperwork helps.
How long does a damp proof course last?
A well installed injection treatment is often guaranteed for 20 to 30 years. Physical courses in sound walls can last the life of the building.
Can a dehumidifier fix rising damp?
No. A dehumidifier helps with condensation and helps walls dry after treatment, but it cannot stop moisture rising from the ground.
Who should I call about damp?
Start with the cause. A roofer or builder for leaks, gutters and pointing; a damp specialist or independent surveyor for suspected rising damp; and a plasterer once the wall is dry. For condensation, you may not need anyone at all.
Should I paint over damp patches?
Not until the cause is fixed and the wall has dried. Damp resistant paints only hide the symptom, and the patch will come back through.
Get Quotes
Use the form at the top of this page to get quotes from local specialists. Ask each one how they diagnosed the problem, what is causing it and exactly what they propose to do, then compare the answers as carefully as the prices.
Checked October 2026. Sources: Checkatrade damp proofing cost guide (2026 prices), damp proof course cost breakdown and tanking cost guide; Property Care Association guidance on surveyor qualifications.