How to clean mould off a wall safely

You can clean a small patch of mould at home, wearing gloves and a mask and with the window open. Use water with washing-up liquid or a product made for mould, scrub carefully and dry well. If the mould is extensive or keeps coming back, leave the cleaning to a professional.

Protect yourself first

When you scrub mould, spores are released into the air. You do not want to breathe them in or get them on your skin or in your eyes. So:

wear rubber or nitrile gloves;
wear a mask that covers your nose and mouth. An FFP2 mask is better than a simple cloth mask;
wear safety goggles, especially if you are cleaning a ceiling;
open the window and keep the door of the room closed, so the spores do not spread to the rest of the home;
wear clothes you can wash straight afterwards.

If you have any doubts about the effect of mould on someone's health in your household, speak to your doctor.

What you need

a bucket of warm water with a little washing-up liquid;
a soft sponge or brush;
cloths you can throw away;
bin bags;
if you like, a product made for removing mould, used according to the instructions on the packaging.

Step by step

Cover the floor and furniture with plastic sheeting or old cloths.
Dampen the stain with a cloth or a spray bottle. This puts less dust and fewer spores into the air.
Scrub with the water and washing-up liquid, without soaking the wall.
Wipe with a clean damp cloth to remove any residue.
Dry well with a dry cloth and leave the window open. If you can, use a dehumidifier or heating in the room.
Put the cloths and sponges in a bag, seal it and throw it away.
Wash your hands and the clothes you wore.

What to avoid

Do not mix cleaning products. Mixing bleach with other products, such as ammonia or drain cleaners, can release dangerous gases.
Do not sweep or vacuum dry mould with an ordinary vacuum cleaner. It spreads the spores.
Do not use too much bleach or use it without ventilation. On porous walls, bleach may not reach deep into the material and leaves the wall wet.
Do not wet the wall too much, because the extra moisture helps the mould come back.
Do not paint over it without cleaning and drying first.

When it is best to call a professional

the stain is large, for example longer than your arm, or covers several walls;
the mould comes back soon after being cleaned;
the wall is wet, the plaster is soft or the paint is peeling;
there is a strong musty smell and you cannot see where it comes from;
you have small children, pregnant women, elderly people or people with breathing problems at home. In these cases it is better not to clean it yourself.

In these cases, the most important thing is to find out why the wall is damp. Cleaning is only the first step.

After cleaning

Wait until the wall is completely dry. In some cases, this takes several days. Then you can apply a primer and paint. Before painting, deal with the cause of the damp, otherwise the mould will return.

Tip: Check the wall with your hand after a few days. If it still feels cold and damp to the touch, it is not ready for painting yet.

To stop the mould coming back, ventilate your home every day, do not push furniture against cold walls and try to keep the temperature steady. In damper areas, such as the Sintra mountains, these habits are even more important.