A damp proofer (also called a damp proofing specialist or damp and timber specialist) identifies the source of moisture in buildings and applies appropriate treatments. The three main causes of damp - rising damp, penetrating damp and condensation - each require a different solution, and a good specialist will always survey before recommending treatment. Common treatments include chemical damp proof course (DPC) injection for rising damp, tanking systems for basement waterproofing and improved ventilation for condensation. PCA (Property Care Association) registration is the key quality mark for this specialist trade.
What they do
- Damp survey and diagnosis - rising damp, penetrating damp, condensation
- Chemical damp proof course (DPC) injection
- Tanking and basement waterproofing
- Cavity wall drainage systems
- Waterproof render and renovation plaster
- Timber treatment for wet and dry rot
- Ventilation installation to combat condensation
- Reports for mortgage lenders and property buyers
When you need one
Damp problems can cause serious structural and health issues if untreated. Always get an independent survey before agreeing to any remedial work.
Typical costs (UK, 2025)
| Job type | Typical cost |
|---|---|
| Chemical DPC injection (per wall) | £300 - £600 |
| Full rising damp treatment (terrace house) | £1,500 - £4,000 |
| Basement tanking (per sq m) | £70 - £150/sq m |
| Cavity drain membrane system (per sq m) | £50 - £100/sq m |
| Wet rot treatment | £500 - £2,000 |
| Independent damp survey | £150 - £400 |
Costs do not include replastering, redecoration or structural repairs to address the root cause of the damp. Always address the underlying cause before treating the symptoms.
Qualifications to look for
The PCA is the trade association for damp proofing, timber treatment, structural waterproofing and flood remediation. PCA members are audited for technical competence and must carry professional indemnity insurance. Find a PCA member at pca.org.uk.
The CSRT is a professional qualification from the PCA for surveyors specialising in damp and timber diagnosis. A surveyor with CSRT designation has demonstrated competence in diagnosis as well as treatment.
How to find a reputable damp proofer
Frequently asked questions
How do I know if I have rising damp or condensation?
Rising damp typically appears as a tide mark 1-1.5 metres above floor level, often with salt staining (efflorescence) and peeling plaster. Condensation usually appears at higher levels - on cold surfaces such as window reveals, corners of rooms and north-facing walls. A PCA-registered surveyor uses a moisture meter and will take samples for laboratory analysis to distinguish between the two.
What is a chemical DPC injection?
A chemical damp proof course (DPC) injection involves drilling holes along the base of the wall and injecting a water-repellent silane or siloxane fluid that diffuses into the masonry and creates a moisture barrier. The holes are then re-pointed. The work typically carries a 20-30 year guarantee when installed by a PCA-registered company.
Will I need to replaster after damp treatment?
Usually yes. After rising damp treatment, the salt-contaminated plaster must be removed to a height of around 1 metre and replaced with a renovation plaster or damp-resistant render that resists the residual hygroscopic salts in the wall. The new plaster cannot be decorated for several months while it dries fully.