Can you paint over mould?

Why paint alone does not stop mould

Mould needs moisture. When you paint over it, the new coat covers the stain but does nothing about the damp that let it grow, so the patch can show through again. A fresh coat on its own is a cosmetic fix, not a repair.

The mould can also point to a bigger problem. PUB lists mould, discolouration and peeling paint on walls, floors or ceilings as signs of a leak at home, along with unusually high water bills and the sound of running or dripping water at night when nothing is in use.

Find and fix the moisture source

If you see mould on ceiling paint below an upstairs toilet or bathroom, check for a leak from the flat above first. HDB explains that ceiling leaks happen when water from the flat above seeps through the floor slab, usually from wear and tear of the waterproof membrane and screed, and typically occur in toilets and bathrooms. Untreated ceiling leaks may cause mould growth, and HDB says neighbours should address a leak promptly.

Inside your own flat, try the meter test from PUB's tips on finding leaks. Turn off all taps and water-using appliances, then watch the water meter for at least 10 minutes. If the dial moves, there is a leak. Also look for water stains, mould or peeling material under the sink.

If no leak turns up, look at airflow: one of HDB's preventive measures for walls is to facilitate cross-ventilation in the flat. For help tracing a leak, see leak repair, and for dealing with the flat above, read what to do about a ceiling leak.

How to paint over mould: prepare the surface first

Work in this order. These are practical steps rather than official rules, so agree the details with your painter for the room and the product.

1. Fix the source. Repair the leak or damp first, or the mould can show through the new paint.
2. Ventilate the room. Open doors and windows before you start and keep them open during and after cleaning.
3. Clean the surface. Use a suitable product and follow its label for preparation, contact time and protective equipment.
4. Let it dry fully. Give the wall or ceiling time to dry right through before any paint goes on.
5. Repaint. Apply the paint you and your painter have chosen, following the product's instructions.

NEA's guidelines for cleaning homes say to apply disinfectants according to the manufacturer's guidelines, give the stated contact time and use the protective equipment the product's Safety Data Sheet prescribes. NEA lists hypochlorites, such as household bleach (sodium hypochlorite), as fungicidal, and recommends ventilating the home during and after cleaning.

This page focuses on painting. For cleaning methods in more detail, see our guides on removing bathroom mould and mould on the ceiling.

Anti-mould paint: what to ask

None of the official sources on this page rate anti-mould paints, and no paint fixes the leak or damp behind a mould patch. Before work starts, ask your painter:

• Which product do you propose for this wall or ceiling?
• Is it meant for interior wet areas such as bathrooms?
• Can I see the product's data sheet?
• Does the quote include cleaning, drying time and the number of coats?

Not sure who to hire? See whether a handyman or painting contractor suits your job, or browse painting services in the directory. To estimate how much paint the wall or room needs, try the paint calculator.

Keeping it from coming back

HDB's guide to wall cracks lists two preventive measures: facilitate cross-ventilation in the flat and re-paint the walls regularly. For hairline cracks, HDB says to re-paint the wall with a flexible sealant or elastomeric paint.

For everyday airflow, NEA says occupants of homes may improve ventilation by opening doors and windows, and that fans can be used to promote air circulation when needed.

HDB's guide to ceiling leaks also suggests using non-corrosive detergents in toilets and bathrooms, and mopping rather than washing the kitchen floor, as there is no waterproofing membrane under kitchen tiles.

When to stop and call a professional

Call a professional if the leak comes from the flat above, the wall has wider cracks, the mould returns after cleaning or it covers a large area.

For a leak between two flats, HDB sets out the steps: talk to your upstairs neighbour, agree on a time for a check, engage a contractor jointly to confirm the source and recommend a repair method, then split the cost. HDB says you negotiate price and scope with the contractor yourself.

For wider cracks, HDB says to engage a contractor. To detect and repair leaks, PUB says to always engage a licensed plumber. The cost depends on the job, so compare published prices on handyman rates.

Questions