How to Stop Condensation and Mould Before Painting
Paint never fixes damp — it only survives it. Here's how to diagnose the cause, cut the moisture and treat mould properly before the first coat goes on.
Condensation, Penetrating Damp and Rising Damp Are Not the Same
Before a brush touches the wall, you need to know which problem you actually have. Condensation appears on cold surfaces, usually around windows, in corners and behind furniture, and is worst in bathrooms and bedrooms in winter.
Penetrating damp comes from outside — failed pointing, a cracked render, a blocked gutter or a leaking overflow. It usually shows as a defined patch that darkens after heavy rain.
Rising damp climbs from ground level, tends to stop at a tide mark around a metre up, and often leaves salt deposits behind. Each of these needs a different fix, and none of them are solved by paint.
Heat, Ventilate, Then Keep It Steady
Condensation is a balance between warm humid air and cold surfaces. Low, constant background heating warms the walls so moisture stops settling on them — far more effective than short blasts of high heat.
Ventilation removes the moisture itself. Working extractor fans in the kitchen and bathroom, trickle vents left open, and internal doors kept open so air can move all make a measurable difference within days.
In empty properties, run heating at a modest steady setting for several days before work starts. A cold, sealed vacant flat is the ideal environment for mould and the worst possible one for fresh paint.
Kill the Mould — Never Paint Over It
Mould must be treated with a proper fungicidal wash, left to work for the stated time and then allowed to dry fully. Wiping with household cleaner spreads spores; painting over living mould guarantees it returns through the new coat.
Blown or soft plaster needs cutting back to a sound surface. Stained areas need a stain-blocking primer so old marks don't ghost back through your finish weeks later.
Only once the wall is dry, sound and treated should you prime and paint — ideally with an anti-mould or breathable emulsion suited to the room. Do it in that order and the finish holds for years instead of months.
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