Damp is one of the most common problems in UK homes — and also one of the most misdiagnosed and overcharged for. Understanding the type of damp you have is essential before spending money on treatment.
Three Types of Damp
1. Rising damp
Moisture rising from the ground through the walls due to a failed (or missing) damp-proof course (DPC). Signs: tide mark on the wall up to ~1 metre, peeling wallpaper, crumbling plaster.
Important: true rising damp is relatively rare. Many cases diagnosed as rising damp are actually penetrating damp or condensation. Always get a second opinion before agreeing to a chemical DPC injection.
2. Penetrating damp
Water entering through the walls or roof from outside — through cracked rendering, damaged pointing, leaking gutters, or defective flashing. Signs: damp patches that get worse after rain, usually on upper floors or external walls.
3. Condensation
The most common type of damp in UK homes. Warm, moist air condenses on cold surfaces, leading to black mould. Caused by poor ventilation, drying clothes indoors, or lack of heating. Signs: black mould around windows, in corners, and behind furniture.
What Each Type of Damp Costs to Fix
| Damp Type | Typical Fix | Typical Cost |
|---|---|---|
| Condensation | Improve ventilation (extractor fans, PIV unit) | £200–£1,200 |
| Penetrating damp | Fix the source (repointing, rendering, gutter repair) | £300–£2,000 |
| Rising damp | Chemical DPC injection + replastering | £1,500–£4,000 |
The Biggest Mistake: Treating the Symptom, Not the Cause
The most expensive mistake with damp is paying for a treatment that doesn't address the actual cause. A chemical DPC injection won't fix penetrating damp caused by a leaking gutter — but some companies will sell it anyway. Before agreeing to any damp treatment:
- Identify the type of damp — a damp meter alone isn't enough; look for the source of moisture
- Fix the cause first — repair gutters, improve ventilation, fix leaks
- Only then treat the effect — replaster, apply damp-proof membrane, or inject DPC if genuinely needed
When to Get a Damp Survey
A professional damp survey costs £150–£300 (some companies offer free surveys, but be wary of the sales bias). An independent surveyor (not a company that also sells treatment) gives the most honest assessment. Look for a CSRT (Certificated Surveyor in Remedial Treatment) qualified surveyor.
Replastering After Damp Treatment
After any damp treatment, the affected plaster usually needs to be removed and replaced with a salt-resistant renovating plaster. This is a significant part of the cost — don't accept a quote that only covers the DPC injection without including replastering.