Damp proofing cost: what the job involves and who is registered to do it

How damp proofing cost works

1. Establish that it is rising damp at all. Rising damp is far less common than the number of quotes for it suggests, and penetrating damp from a failed gutter, a raised path or a bridged cavity produces a similar tide mark. A survey that does not rule those out before recommending a chemical course is selling a product rather than diagnosing a fault.
2. Measure the run, not the room. The course is priced per linear metre of wall treated, so the quote should state the runs it covers and their lengths. Two quotes that differ by a third usually differ because one of them is treating an internal partition the other has left alone.
3. Ask how high the plaster comes off. Salt-contaminated plaster has to go, and how far up is a judgement the surveyor makes. It is the single line that most often separates two prices, and it should be written down rather than settled on the day by whoever is holding the bolster.
4. Agree the drying time before the replastering. A wall that is replastered before it has dried pushes the same salts back through the new finish. The industry rule of thumb is roughly a month per twenty five millimetres of wall thickness, and a programme that skips it is buying a callback.
5. Check what the guarantee actually covers. Most guarantees cover the injected course and not the replastering, which is where the visible failure shows. Read which of the two the certificate is about, and whether it is insurance backed against the firm ceasing to trade.

Insurance and paperwork

Common questions

Why do damp proofing quotes vary so much?

Because they are rarely quoting the same job. The injection is a small part of the cost; the plaster removal height, the number of walls, whether floors come up and who reinstates decoration are the variables. Compare the itemised lines rather than the totals.

Do I need a damp course if the house is Victorian?

Not necessarily. Many Victorian houses have a slate or bitumen course that is still working, and moisture at the base of a wall is more often a raised external level, a blocked airbrick or a leaking downpipe. Those are cheaper to fix and should be excluded first.

Is a damp survey from the contractor who wants the work independent?

It is not, and that is worth saying plainly. A free survey from a firm that sells damp courses is a sales visit with a moisture meter. An independent damp and timber surveyor who does no remedial work charges a fee and has nothing to sell you.

Registered contractors by region

• Registered roofers in the East Midlands postcode area
• Registered roofers in the East of England postcode area
• Registered roofers in the London postcode area
• Registered roofers in the North East postcode area
• Registered roofers in the North West postcode area
• Registered roofers in the Scotland postcode area
• Registered roofers in the South East postcode area
• Registered roofers in the South West postcode area
• Registered roofers in the Wales postcode area
• Registered roofers in the West Midlands postcode area
• Registered roofers in the Yorkshire and The Humber postcode area