Does mould die without moisture? The science, simply

No: it stops growing, but it doesn't die

Take the moisture away and mould stops growing. The colony dries out, stops spreading and can look faded or powdery. That isn't the same as dead. Mould spores are built to survive dry periods; they can sit on a surface or in dust for a long time and start growing again once moisture returns. Drying a room stops the damage getting worse, but on its own it doesn't get rid of the mould.

What mould needs to grow

Mould needs food, a suitable temperature and moisture. The food is almost everywhere in a home: dust, paint, wallpaper paste, plaster, timber, fabric and leather. Most homes stay at a temperature mould is comfortable with all year. That leaves moisture as the one condition you can realistically control, and it's why every lasting fix starts by finding out where the water comes from.

The moisture doesn't have to be a puddle. A wall wetted by condensation every night, a damp patch fed by a slow drip, or air that stays humid for weeks is enough.

Why dried-out mould comes back

Mould that has dried out is dormant. Its spores and fragments stay on and in the surface, and many are tough enough to outlast a dry summer. When conditions return, whether that's the first cold, damp weeks of winter, a humid spell by the coast, a blocked air-conditioner drain or a drip under a sink, growth can restart from what was already there, usually in the same spot. That's a large part of why mould comes back after cleaning when the moisture source was never dealt with.

In Cyprus the cycle is easy to miss. A bedroom wall can look clean through the dry months, then the same black patch reappears each winter.

Do you still need to remove dead or dormant mould?

Yes, for three reasons. First, dried mould still releases spores and particles when it's disturbed by cleaning, brushing past it or a draught. Mould can irritate the airways and can make asthma and allergies worse whether it's growing or not; the guide to mould, asthma and allergies covers this. If anyone at home has symptoms you think may be linked, speak to your GP.

Second, whatever is left on the surface is ready to grow again the next time it gets damp. Leaving it means relying on that spot staying dry for good.

Third, it's evidence. Old mould shows where moisture got in, and that problem may not be solved just because the patch has stopped spreading.

Removing dormant mould properly

Treat dry mould with the same care as active growth. Open a window, wear gloves and a mask, and keep children and pets out of the room. Don't brush or vacuum dry mould off a wall, because that throws spores into the air. Instead, lightly dampen the area and wipe it with a mould cleaner, then bag the cloths and bin them. Don't mix cleaning products. Let the surface dry fully afterwards. The guide to removing mould from walls goes through the steps.

Before you redecorate, make sure the wall is dry inside, not just dry to the touch, and that whatever wet it in the first place has been fixed. Painting over old mould only hides it under the new finish.

When drying and cleaning aren't enough

Hard, sealed surfaces such as tiles, glass and gloss paint usually clean up well. Porous materials are different. Mould grows into plaster, plasterboard, grout, timber, fabric and mattresses, so wiping the face leaves growth behind, waiting for the next damp spell. Soft items with deep mould are usually best replaced.

For staining that has soaked into plaster, or patches that keep returning, we find the cause before we touch the mould, so the fix lasts. Treatment for a dried-out patch that keeps reappearing is usually one visit with no building work. Where the growth has worked into the wall, removal of mould that has got into the plaster means the growth is removed, the cause repaired and the surface finished in an anti-mould system.

Keeping it dormant for good

Because spores never fully go away, the long-term answer is keeping surfaces dry. Air rooms daily, use extractors in kitchens and bathrooms, dry washing outdoors where you can, run a dehumidifier in rooms that stay damp, and deal with drips and stains as soon as you spot them. Homes that struggle every winter can use a maintenance plan, from €45 a month, with a monthly visit that keeps humidity down and catches regrowth early.

Not sure whether your mould is active or just dormant? book an inspection from €75 and we'll measure the moisture and tell you exactly where you stand — or call +357 99 759144.