Painting over mould: fix the cause first
Why mould comes back through new paint, and the steps that stop it.
Painting straight over mould almost always fails. Spores keep growing under the new paint, and within weeks the black spots return.
Find the cause
Most mould in London homes comes from condensation: warm, wet air meeting cold walls. Leaks, failed seals and penetrating damp cause the rest. Our guide to condensation, damp and mould explains how to tell them apart.
Treat the mould
Affected areas are cleaned with a fungicidal wash and left to dry fully. Wiping mould with bleach removes the colour but often not the growth.
Seal and prime
A stain-blocking, mould-resistant primer stops old marks showing through. Zinsser primers are one example we use.
Finish with the right paint
In bathrooms, kitchens and cold bedrooms, a moisture-resistant topcoat helps. Ventilation helps most: extractor fans, trickle vents and opening windows after showers and cooking.
For landlords, a written note of what was treated and how is useful evidence for your records.
Where mould comes from
In most homes we visit, mould on walls and ceilings is caused by condensation: warm, moist air from cooking, showers and drying clothes meeting a cold surface. Less often it is a leak, a blocked gutter or damp rising from the ground. The pattern is a clue. Mould in corners, behind furniture and around windows usually means condensation. A single spreading stain usually means a leak.
What we do before painting
- Find and deal with the source, or tell you who needs to
- Kill the mould with a fungicidal wash and let the wall dry fully
- Seal any staining with a stain-blocking primer
- Finish with a mould-resistant paint in kitchens and bathrooms
Keeping it away
Use the extractor fan while cooking and showering and for twenty minutes afterwards. Keep trickle vents open, leave a small gap behind wardrobes on outside walls, and heat rooms steadily in winter. If a fan is weak or missing, fitting a proper one is often the single most useful fix.
For landlords
Damp and mould reports need a prompt, recorded response. We can inspect, photograph, treat and redecorate, and give you a short written note of what we found and did.