Mould and damp in your holiday home: a humidity problem, not a dirt problem

When people see dark patches in their holiday home, the first thought is that the place is dirty. But mould on the West Coast is almost always a humidity problem, not a dirt problem. A closed-up house, damp salty coastal air and big temperature swings cause condensation, especially in the off-season and shoulder season. It is about moisture in the air, not dirty surfaces.

Why it appears right here

When the house stands empty, the temperature drops and damp air meets cold surfaces. Water condenses on walls, in corners and behind furniture. That is why mould often shows up in a house that looks perfectly clean.

A classic trap is bleach (Klorin). Bleach removes the dark stain, but it does not kill the spores deep inside porous materials like wood, plaster and grout. If you do not control the humidity, the mould comes back. Treating the stain alone is a waste of effort.

The hidden spots nobody airs out

The number one spot is closed wardrobes and cupboards against a cold external wall. The air sits still and condensation forms where you cannot see it, until the clothes start to smell.

• Keep wardrobe doors, cupboard doors and interior doors open when the house stands empty, so air can circulate.
• Pull furniture a few centimetres away from external walls so air moves behind it.
• Buy a cheap hygrometer and keep relative humidity under about 60 percent. Almost nobody installs one, yet it is the single best early warning.
• In the off-season, leave a trickle vent or a window notch open. A fully sealed house in winter grows mould.
• Wipe the rubber seals on your washing machine and dishwasher, and leave the doors ajar between visits.
• Stand mattresses and seat cushions on their edge, or raise them off cold surfaces, so they do not sit flat collecting condensation.

If you have to treat real mould

Wear a mask, and do not dry-brush the mould, because that flings spores into the air. Wipe it down gently and ventilate well afterwards. If the growth is large or deep in the material, have a professional look at it.

The safest fix is catching damp early. Our summer house cleaning keeps an eye on the vulnerable spots, and our off-season holiday-home checks catch damp before it spreads. Contact us to ask about an off-season check.