Householders could be spending hundreds of pounds on unnecessary damp-proofing treatment, a consumer watchdog has said.
An undercover investigation by Which? into advice given by damp-treatment companies showed that in two-thirds of cases companies recommended what experts deemed to be unnecessary or inappropriate treatment - or missed the problem completely.
Which? borrowed two houses with a total of three potential damp problems and asked 11 companies - six major and five smaller firms - to visit each home.
"We hoped they would identify and solve the issues," an article in January's edition of Which? said. "But instead we found our visits riddled with dodgy advice and questionable recommendations."
In the first property, five of the 11 companies that visited recommended unnecessary treatment - in one case costing as much as £1,440 - when they should have suggested getting a plumber in to fix a leak, Which? said.
In the second house, only two companies recommended a suitable solution for penetrating damp in the hall.
Which? executive director Richard Lloyd said: "People could be left massively out of pocket by the dodgy advice given by these damp-proofing companies.
"At a time when many people are struggling with their finances, this is simply unacceptable."
© 2011 Press Association