A moisture meter shows where the wall is wet but not where the water comes from. Where the picture is unclear, an on-site building survey is worthwhile.

•  Damp patches start immediately above the floor and run across the wall as a horizontal band: indication of rising damp.

•  Mould sits in room corners, on external walls, behind furniture or on window reveals and appears mainly in the colder months: indication of condensation.

•  A patch grows quickly, stays local and the wall is distinctly wet there: indication of a leak.

•  Damage appears on the cellar wall and worsens after rain: indication of seepage from outside.

•  It does not repair structural defects. A missing damp-proof course, a leaking gutter or a crack in the façade will remain.

•  Existing dark staining does not disappear on its own. Once the wall is dry, it has to be removed mechanically or covered cosmetically.

•  It does not heat a room. The panel is designed for the wall surface, not for the room air.

For rising damp, a retrofitted damp-proof course is the correct measure, either as a mechanical barrier or by injection. For seepage against a cellar wall, external vertical tanking or curtain injection is required. Where there is a leak, repair comes first.

In all three cases Mould DRY can be used sensibly after the remedial work, to dry the wall out and keep it dry. Before that work, it cannot.