Q: "We have a poorly ventilated house and our walls are often affected by condensation, which has led to mouldy patches in some places. We are now redecorating. Is there anything I can do to prevent the problem from recurring, and what is the best sort of paint to use?"
Sophia, London
A: "To help resolve any damp, check all sources of water ingress. Look for overflowing gutters and small cracks in the exterior walls of the property, as these will allow water to penetrate through the walls and into your home. If you find any problems outside these need to be repaired or all the hard work you carry out redecorating will only last a short period of time.
"A lot of damp could simply be condensation. The warm air in the house contains moisture which condenses on any surface which is cooler. Bathrooms and kitchens are more susceptible to condensation, which if left can result in mould growth. Exterior walls are colder and therefore particularly susceptible.
"When it comes to redecorating, you will first need to remove any mould. For this you can use Polycell Mould Killer, which contains a powerful fungicide for killing and removing mould and also helps prevents re-growth. Once the mould has been removed, Polycell One Coat Damp Seal, which has been specially formulated to seal damp patches on interior walls and ceilings, can be used. You will then be able to redecorate your walls and ceilings with standard Dulux paints.
"If the problem persists you may need to consult a builder or look into using decorating materials that can help insulate your internal walls."
Matt GrayAnswer provided by Matt Gray, technical training consultant at Dulux.