Damp, Condensation and Ventilation

What is damp and condensation?

Damp is three different problems that look alike on a wall. Condensation forms when warm, moist indoor air meets a cold surface: it shows as black mould in corners, behind furniture, around window reveals and on north-facing bedroom walls. Penetrating damp comes in from outside through a leaking gutter, failed pointing, cracked render or a bridged cavity, and gets worse after rain. Rising damp is ground water drawn up through the base of a wall where the damp proof course has failed or been bridged, and rarely goes higher than about a metre. Treating the wrong one wastes money, which is why the survey comes first.

In London, Surrey, Kent and Hertfordshire the great majority of damp complaints are condensation. Solid brick Victorian and Edwardian walls, uninsulated 1930s semis and ex-council flats all have cold surfaces, especially at corners, window reveals and the junction of wall and ceiling where the structure bridges the insulation. Add a family drying washing indoors, modern draught-free windows and a bathroom fan that was never wired in, and mould follows every winter. The fix is to warm the surface, cut the moisture and move the air, not to keep painting over it.

Stay Warm surveys the house, measures wall moisture and surface temperature, checks the gutters, pointing, cavity and damp proof course, and tells you which kind of damp you have. Our own team fits extractor fans, positive input ventilation units, air bricks and trickle vents, and installs the internal or external wall insulation that removes the cold surface. Where the diagnosis is rising damp or a structural defect, we arrange and project-manage the treatment through an accredited specialist damp proofing partner and stay your single point of contact.