Genuinely occurs, but is diagnosed far more often than it is present. It requires porous masonry, a source of ground moisture, and a damp proof course that is absent, failed or bridged. Height is self-limiting because capillary rise is balanced against evaporation from the wall face, which is why it rarely exceeds about one metre and produces a horizontal tide mark rather than a diffuse spread. Most damp attributed to it is condensation or penetrating damp.
Related terms
- Damp proof course (DPC)A barrier built into a wall to prevent ground moisture rising through it.
- Hygroscopic saltsSalts in masonry that absorb atmospheric moisture, producing damp readings and staining after the original source is gone.
- CondensationMoisture depositing on surfaces that are at or below the dew point of the surrounding air.
Seeing this in your building?
The free diagnostic works out the mechanism from what you can see and measure, and tells you what it cannot conclude.