High Damp Meter Reading Behind Peeling Plaster: Survey Findings

During a recent damp survey we recorded a high moisture meter reading in an area of wall showing peeling paint, blown plaster and visible salt staining. The evidence together - not any single reading in isolation - is what tells us what is really happening in the wall.

What the damp meter is actually showing

A protimeter or pin-type meter measures electrical resistance close to the surface. A high relative reading in an area with salting and blistered plaster usually means the wall has been wet for a prolonged period. Hygroscopic salts drawn out of the masonry attract moisture from the air, which keeps the surface damp even when the original source has stopped. That is why a single spray-on treatment rarely lasts.

Likely causes on this property

We considered several possibilities: bridged or missing damp proof course, external ground levels sitting too high against the wall, a defective gutter or downpipe soaking the masonry from outside, or a plumbing leak on the other side of the wall. Each leaves a slightly different pattern, and we cross-check readings, external inspection and internal evidence before concluding.

In this case the pattern of moisture, the height above floor level and the condition of the external elevation all pointed to a specific defect rather than generalised rising damp - which is far less common than most homeowners are told.

Our recommendations

Fix the source first, always. That means repairing the external defect or leak, allowing the wall to dry, then removing contaminated plaster back to sound masonry. Re-plaster with a specification suitable for salt-loaded walls, and only redecorate once moisture readings return to acceptable levels. Chemical injection alone, without addressing the actual water source, is not a fix.

Book an independent damp survey

If you have peeling paint, blown plaster or tide marks on a wall, an independent damp survey will identify the real cause with evidence - not a sales quote for a treatment you may not need. Get in touch to arrange an inspection.