While most mould or mildew does not contain the dangerous mycotoxins, all mould can trigger asthma or cold-like symptoms in susceptible people. Mold is not healthy. Black mould can be removed from painted drywall but if the drywall is unpainted, it should be replaced as you will never get the mould out from inside or behind the drywall.
- Skill level:
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Things you need
- Latex or rubber gloves
- Safety goggles or glasses
- Plastic sheeting
- Masking tape
- Clean bucket
- Chlorine bleach
- Dishwashing detergent
- Old clean towels
Assess the drywall. If the black mould is heavy and extensive, the drywall wet through, bowed out, or crumbling, the drywall needs to be removed and replaced because the mould cannot be completely removed. Search this site for directions on how to remove mouldy drywall or call a professional. If the mould is just a speckling on the painted surface such as is common in bathrooms, it can be removed safely and completely.
Protect yourself from disturbed mould spores and caustic chlorine bleach solution while removing mould. Wear an OSHA approved respirator, not one of the paper dust masks which won't protect you from spores or fumes. Wear eye protection, especially if working overhead on a ceiling. Since even a mild bleach solution can burn and irritate your skin, wear protective gloves as well.
Protect surrounding surfaces since bleach can ruin fabrics and carpet. Use plastic, taped into place. Cover that with old towels or dust sheets to hold it in place if you are going to walk on it.
Add about half a cup of household chlorine bleach to a gallon of water. For heavily soiled or dirty areas, up to 1 1/2 cups of bleach may be added to the water but no more than that. Sponge the mixture thoroughly onto the mouldy areas and let it sit for at least 15 minutes.
Add a little dishwashing detergent to clean water and wash the area down. Then rinse it completely with clean water and dry it with old towels.
The drywall should now look clean with no sign of black mould. The cleaning may have discoloured it and if you need to repaint, use only water based primer and paint because oil based paints contain organic compounds that provide nutrients for mould to grow on. If the mould keeps recurring you should install a venting system or a dehumidifier in the area because mould thrives in humid environments.
Tips and warnings
- If the mould is along the bottom of the wall, it is probably also behind the baseboards and under the carpet. You will have to remove the baseboards and pull up the carpet to completely remove it.
- Never mix ammonia based cleaners with chlorine bleach as this can cause toxic chlorine gas.