Quick answer
Open the windows, put on gloves, goggles and an FFP2 mask and treat the mould without dry scrubbing. Wash with soapy water and apply white vinegar, or a specific anti-mould spray, leaving it to work for 15 minutes. Rinse, dry completely with ventilation, apply a fungicidal or anti-mould primer and repaint. Never mix bleach with vinegar or ammonia. If the patch is over 1 m² or returns, treat the cause.
What you need
- Rubber gloves, safety goggles and an FFP2 mask
- Cloth, sponge and bucket
- Spray bottle
- Filling knife and 120 grit sandpaper
- Short-pile roller and brush
- Dehumidifier (optional)
- Water with mild soap
- White vinegar or a specific anti-mould spray (from Mercadona, Leroy Merlin or Bricodepot)
- Fungicidal or anti-mould primer (Zinsser, Bruguer, Montó or Titan)
- Anti-mould emulsion (Bruguer, Montó or Titan)
- Bin bags and masking tape
Step by step
- 1
Ventilate and protect yourself
Open windows and doors, take children, asthmatics and pets out of the room and put on gloves, goggles and an FFP2 mask. Do not use a fan, which would blow spores into other rooms.
- 2
Isolate the area
Cover furniture and the floor with plastic sheeting. Do not sweep or vacuum the patch dry.
- 3
Measure the patch
If it is over 1 m² or the wall is soft or damp, stop here and consult a professional. If it is smaller and the wall is firm, carry on.
- 4
Dampen and clean
Spray the area with water and mild soap and go over it with the sponge without scrubbing hard. Collect the dirt with the cloth and throw it into a sealed bag.
- 5
Apply the anti-mould
Spray on neat white vinegar or a specific anti-mould spray and leave it to work for 15 minutes. Do not mix it with bleach or ammonia. If you use bleach instead of vinegar, dilute it and do not have used any other product first.
- 6
Rinse and dry
Wipe with a cloth and clean water to remove residue and leave it to dry with the windows open. If you have a dehumidifier, run it for 6-8 hours. The wall must be dry to the touch before painting.
- 7
Sand the damaged areas
If the paint is lifting or the patch has left the plaster soft, scrape with the filling knife and sand with 120 grit. Vacuum the dust with your mask on and wipe with a damp cloth.
- 8
Prime with fungicide
Roll on one coat of fungicidal or anti-mould primer. Leave it to dry for 4 to 6 hours, as the tin says.
- 9
Repaint with anti-mould paint
Apply two coats of anti-mould paint, with 4 hours between coats. Seal the corners well, which is where it usually returns.
- 10
Keep an eye on the cause
Over the following weeks, check whether it reappears. Keep up daily ventilation, keep humidity below 60% and move furniture away from the wall. If it comes back within a month, there is an unresolved cause and you need a specialist.
Why mould appears on a wall: diagnose before you clean
Mould is a fungus that needs damp and poor ventilation. If you clean it without knowing where it comes from, it comes back. Look at where the patch is, because its location almost always reveals the origin.
Condensation: black or greenish spots in corners, behind wardrobes, on the cold wall of a north-facing room and around windows. It is the most common cause in closed-up flats or flats with little ventilation. Leaks: a patch with a brown edge and a wall that feels damp to the touch, near bathrooms, kitchens, downpipes or terraces. Rising damp: appears at skirting board level, up to 1 m high, and often leaves white salts (salitre) on ground floors and in older houses.
| Where it appears | Probable cause | What to do |
|---|---|---|
| Corners, behind wardrobes, beside windows | Condensation and poor ventilation | Ventilate, use a dehumidifier, move furniture off the wall |
| Under windows or on the ceiling, with a brown stain | Water leaking in from outside or from the terrace | Check the seals and call a specialist |
| Near bathrooms, kitchens and downpipes | Pipe leak or splashing | Find the leak with a plumber |
| Skirting level on ground floors, with white salts | Rising damp | Specific treatment, painting is not enough |
| Cold exterior wall | Thermal bridge | Anti-mould paint and constant ventilation |
Safety: what not to do with mould
Mould releases spores that you can breathe in. Do not scrape it dry or sweep it. Open the windows and wear rubber gloves, goggles and an FFP2 mask, which filters spores better than a surgical one.
Never mix bleach with vinegar or ammonia. They give off chlorine and chloramine, toxic gases that irritate the lungs and can put you in A&E. Use one product at a time and rinse well before applying the next. If you use bleach, dilute it and never use it in a closed space.
Do not clean the mould yourself if there are small children, or asthmatic or allergic people at home who cannot leave for a few hours, or if the patch is larger than 1 m². In those cases it is better to call someone who will treat the cause and clean with the right equipment.
Common mistakes when removing mould
These mistakes make the mould return or leave you with a worse wall:
- Painting over it without cleaning. Mould grows through the paint and reappears. You have to clean, treat and dry first.
- Using only bleach. It kills surface mould, but not what is in the pores of the plaster, and it whitens the stain without fully removing it.
- Scrubbing dry. It lifts spores and spreads them around the room.
- Not fixing the cause. If there is a leak, water getting in or chronic condensation, the mould returns within weeks.
- Closing up the room to keep air out. Without ventilation mould thrives. Air the room for 10-15 minutes a day even when it is cold.
- Using ordinary paint. Standard emulsion does not stop mould. Use anti-mould paint or a fungicidal primer.
When to call a professional
Call if the patch is larger than 1 m², if it is the second or third time it has appeared, if there are small children or people with asthma, if it smells damp even though the wall looks dry, or if you suspect a leak or water ingress. Cleaning alone is not enough: the cause has to be fixed.
We do not do reformas (full refurbishments) or waterproofing, but we do clean, repair the wall and repaint with anti-mould paint. With the painters service, painting walls costs €6-8/m² and repairing a crack or flaking patch €50-120; hourly work starts at €35-45 for the first hour. If the cause is a leak, you first need a plumber. See more figures in how much it costs to paint a flat. In Torrevieja, Benidorm, Alicante or Valencia we arrive in 20-45 minutes and give a 6-month written guarantee.
Mould on the coast: humidity, salt air and how to prevent it
In flats on the Costa Blanca and in Valencia, the relative humidity of the air often exceeds 70%. If the home is also closed up for most of the year (a second home), mould grows in wardrobes, corners and bathrooms. Leave the roller shutters slightly open, air the place for at least 15 minutes a day when you are there, and put a dehumidifier or anti-damp sachets in wardrobes if you are away for several weeks.
On the seafront, salt absorbs water from the air and keeps exterior walls damp. Together with the damp in the uninsulated stone or brick walls of older houses, it is why mould reappears in the same corners every autumn. The answer is continuous ventilation, an extractor fan in the bathroom and kitchen, and keeping furniture away from the exterior wall: leave a 5 cm gap. If the damp is coming from below, read how to get rid of damp on a wall, and if the mould is in the shower, how to remove mould from the shower.
Frequently asked questions
Which is better for removing mould, bleach or vinegar?
Neither is magic. White vinegar does not damage the wall or give off chlorine and works on small patches; diluted bleach lightens the stain but does not get into the pores. Never mix them or combine them with ammonia: they produce toxic gases. Use just one, ventilate and follow up with anti-mould paint or primer.
Is mould on a wall dangerous to health?
It can be. Spores irritate the airways and make asthma and allergies worse, especially in children and older people. With small patches, protect yourself with gloves and an FFP2 mask. With more than 1 m², recurring mould or sensitive people at home, it is better to call a professional.
Why does the mould come back even when I clean it?
Because the cause is still there: condensation, high humidity in the air, water getting in or a leak. Cleaning removes the symptom, not the origin. Ventilate daily, use a dehumidifier if needed, check the pipes and seals and move furniture away from exterior walls.
Can you paint over mould?
No. Ordinary paint does not kill it and the mould grows back through it within weeks. First it has to be cleaned, treated with anti-mould, left to dry completely and repainted with fungicidal primer and anti-mould paint. If the wall is soft or damp, repair it first.
How much do you charge to remove mould and repaint?
Cleaning the wall and repainting walls costs €6-8/m² and repairing a crack or flaking patch €50-120. Hourly work starts at €35-45 for the first hour. We do not waterproof or do reformas, but we do clean and paint with anti-mould. Fixed price by WhatsApp from photos.