Damp Proofing Cost Guide 2026 | UK Treatment Prices
Discover the true cost of damp proofing in 2026. Whether you are dealing with rising damp, penetrating damp, or condensation, our comprehensive guide breaks down treatment prices, hidden costs like re-plastering, and how to avoid overpaying for unnecessary work.
Quick Cost Estimates (2026)
- Rising Damp (Injection): £500 - £2,500 (depending on re-plastering)
- Condensation Control: £150 - £500 (Vents/PIV units)
- Penetrating Damp: £500 - £3,000 (Repointing/Rendering)
- Damp Survey: £200 - £300
Damp Proofing Cost Calculator
Use our estimator to get a rough idea of what a professional damp proofing job might cost in your area.
Estimates are for guidance only and include VAT. Prices vary by region (London +20%).
1. Understanding the Types of Damp
Before you can estimate the cost, you must correctly identify the type of damp. Misdiagnosis is the most common reason homeowners waste money on damp proofing. Treating a wall for rising damp when the issue is actually condensation will result in zero improvement and a lighter wallet.
Rising Damp
Rising damp occurs when moisture from the ground travels up through the pores in your wall's masonry via capillary action. It rarely rises above 1.2 metres. The key sign is a "tide mark" of salts and dampness at the base of the wall.
Cost implication: Moderate to High. Requires a chemical DPC injection and, crucially, the removal and replacement of salt-contaminated plaster.
Penetrating Damp
This is caused by water entering the property horizontally due to external defects. Common culprits include cracked render, porous brickwork, leaking gutters, or high external ground levels bridging the DPC.
Cost implication: Variable. Can be as cheap as fixing a gutter (£100) or as expensive as re-rendering an entire house (£5,000+).
Condensation
The most common form of damp in modern homes. It is caused by moist air hitting cold surfaces (walls, windows) and turning back into water. Signs include black mould, streaming windows, and a musty smell.
Cost implication: Low to Moderate. Usually solved by improving ventilation (extractor fans, PIV units) and heating.
2. Rising Damp Treatment Costs Explained
The standard treatment for rising damp in 2026 involves drilling holes into the mortar course and injecting a silicone-based cream. This creates a waterproof barrier.
| Work Item | Average Cost (2026) | Notes |
|---|---|---|
| DPC Injection Only | £50 - £80 per metre | Does not include plastering. |
| Plaster Removal & Re-skimming | £60 - £100 per sq metre | Essential for salt-damaged walls. |
| Total for Terraced House | £1,500 - £2,500 | Includes injection and plastering to 1m height. |
| Total for Semi-Detached | £2,000 - £4,000 | Depending on 3 or 4 walls treated. |
The Hidden Cost: Re-plastering
Many homeowners are surprised that the injection itself is relatively cheap. The bulk of the cost comes from the mess. You must hack off existing plaster to a height of at least 1 metre (or 500mm above the highest sign of damp). The wall must then be re-plastered using a salt-retardant mix or a waterproof membrane system. Using standard gypsum plaster will result in the damp returning immediately due to residual salts in the brickwork.
3. Penetrating Damp & Structural Repairs
Unlike rising damp, you cannot simply "inject" penetrating damp away. You must solve the source of the water ingress. The costs below reflect the repair work needed to stop the water.
- Repointing Brickwork: £40 - £60 per square metre. If your mortar is crumbling, water will seep through.
- Applying Water Repellent (Silicone): £10 - £15 per square metre. A breathable seal for porous bricks.
- Gutter Repair/Replacement: £150 - £400. A very common cause of isolated damp patches.
- External Rendering: £50 - £80 per square metre. A full re-render is expensive but provides the ultimate protection.
- Lowering Ground Levels: £300 - £600. If soil or a patio is higher than your DPC, it must be dug out (French drain).
4. Condensation Solutions
If your damp surveyor identifies condensation, do not pay for a DPC injection. Instead, invest in air quality management.
- Passive Vents: £30 - £50 installed. Simple holes core-drilled through walls.
- Humidistat Extractor Fans: £250 - £400 installed. Fans that turn on automatically when moisture is high.
- Positive Input Ventilation (PIV): £800 - £1,200 installed. A unit in the loft that gently pushes fresh, filtered air into the house, forcing damp air out. Highly effective for whole-house condensation.
5. Independent Damp Surveys
Should you get a free survey from a damp proofing company or pay for an independent one?
"Free" Contractor Surveys: These are sales pitches. While some are honest, many are incentivized to find damp where none exists to sell you a £3,000 injection course. Use with caution.
Independent PCA Surveyor (CSRT/CSSW): Cost £200 - £350. These professionals charge for the report but have no financial interest in the remedial work. They often identify simple fixes (like a blocked air brick) that could save you thousands. In 2026, we strongly recommend an independent survey for property purchases.
6. Timber Treatment
Damp walls often lead to wet rot, dry rot, or woodworm in adjoining floor joists and skirting boards. This is often discovered only after plaster is removed.
- Joist Replacement: £300 - £500 per joist.
- Timber Treatment Spray (Fungicide): £300 - £600 per room.
- Dry Rot Eradication: £2,000+. Dry rot is serious and spreads rapidly; it requires extensive masonry sterilization and timber removal.
7. DIY vs Professional
Can you do it yourself?
Injection creams are sold in tubes for standard caulk guns. Drilling holes and injecting the cream is well within the capabilities of a competent DIYer. A DIY kit costs around £100 for a small house.
The Risks:
1. Misdiagnosis: Injecting a wall suffering from condensation is a waste of time.
2. Plastering: The re-plastering requires specific mixes (sand/cement with waterproofer). Standard skimming will fail.
3. Guarantees: You will not get a 20-30 year insurance-backed guarantee with DIY work, which may be required by mortgage lenders when you sell.
Frequently Asked Questions
How much does a damp proof course injection cost?
For a standard terraced house, a chemical injection DPC typically costs between £500 and £1,200 for the injection work alone. However, if re-plastering is required (which is common for rising damp), the total cost often rises to £1,500–£2,500.
Is damp proofing covered by house insurance?
Generally, no. Most standard buildings insurance policies classify rising damp and condensation as wear and tear or maintenance issues. However, if the damp is caused by an 'escape of water' (e.g., a burst pipe), you may be covered for the damage caused, though not necessarily the repair of the source.
How long does a damp proof course last?
Modern silicone cream injections typically come with guarantees ranging from 20 to 30 years. When installed correctly by a Property Care Association (PCA) member, the treatment is often effective for the lifetime of the wall.
Do I really need to hack off the plaster for rising damp?
Yes, in most cases of genuine rising damp. Groundwater contains hygroscopic salts (nitrates and chlorides) that contaminate the plaster. Even if you stop the rising water, these salts attract moisture from the air, keeping the wall damp. Re-plastering with a salt-retardant additive is essential for a dry finish.
What is the difference between rising damp and penetrating damp?
Rising damp moves vertically up from the ground through capillary action in porous masonry, typically stopping around 1 metre high. Penetrating damp moves horizontally through walls due to external defects like cracked render, leaking gutters, or high ground levels, and can appear at any height.
Can I install a damp proof course myself?
DIY kits for chemical injection are available and relatively easy to use (£50-£100). However, the critical part is correctly diagnosing the damp type and the subsequent re-plastering, which requires skill. DIY work also won't come with an insurance-backed guarantee, which can affect future property sales.
How much does a damp survey cost?
A specialized damp survey typically costs between £200 and £300. Some contractors offer 'free' surveys, but independent surveyors (who don't sell treatments) charge a fee to provide an unbiased report. This can save money by avoiding unnecessary work.
About the Author: Mustafa Bilgic
Mustafa is the Lead Cost Estimator at UK Calculator. With over 15 years of experience in the UK construction and renovation sector, he specializes in property pathology and remediation costings. He regularly consults with PCA-accredited surveyors to provide the most accurate pricing data for homeowners.