Damp investigation

Damp is not one condition. It is at least three unrelated ones — rising damp, penetrating damp and condensation — that happen to produce similar-looking marks on a wall. They have different causes, different treatments and wildly different costs. Treating the wrong one does not partially work. It does nothing at all, and you find out six months later when the stain returns.

The industry's incentives make this worse. A firm that only sells damp proof courses will tend to find problems that need a damp proof course. A hand-held conductance meter pressed against a plaster wall will read high for salt contamination, for condensation, for a leaking pipe and for genuine rising damp alike — the number on the screen looks like evidence, but on its own it distinguishes none of those from each other.

An investigation is an attempt to remove that ambiguity before money is committed. It is deliberately sold separately from any treatment, which is the only structural way to keep the two decisions honest.

It starts outside. Ground levels against the wall, the condition of the pointing and render, where the rainwater goods discharge, whether a path or patio has been laid over the damp proof course, whether airbricks are clear. A significant proportion of internal damp is explained entirely by something visible from the garden.

Inside, the pattern of the moisture matters more than any single reading. Height, shape, whether it is worse in a corner, whether it tracks a pipe run, whether it is on an external wall or an internal one, whether it appears in cold weather or wet weather. Rising damp does not appear on a first-floor wall. Condensation does not respect the height of a damp proof course. The distribution is usually more diagnostic than the meter.

Where the evidence is genuinely ambiguous, deeper testing settles it — drilled samples to establish moisture distribution within the masonry rather than at its surface, and salt analysis, because hygroscopic salts left behind by historic moisture will keep a wall reading damp long after the original cause has been resolved.

You get told what it is, what caused it, and what fixing it involves. If the honest answer is that it needs nothing beyond better ventilation and a repointed section of wall, that is the answer you get.

A clear explanation of the cause in plain language, and a fixed-price quote for whatever remedy the evidence supports — agreed in writing before any work begins. If you want that written up formally for a solicitor, a mortgage lender or an insurer, that is a damp survey rather than an investigation.

You are under no obligation to have the remedial work done by me. Plenty of people take the diagnosis, hand it to their own builder, and that is a perfectly reasonable outcome.