While the white powder often found on basement or cellar walls and mould are both caused by similar conditions, they are actually different materials. The white powder is efflorescence or minerals left behind as water that has flowed through the concrete walls evaporates. Mould is a living organism that occurs in wet environments. Both can be cleaned. The first step in the process is drying out the wet conditions in the basement.
Remove white powder
Scrub the walls with pure white vinegar. Use a stiff brush to apply the vinegar, which will dissolve the mineral content of the white powder on the wall.
Rinse the vinegar mixture off the walls. Use a power washer or simply wash with a brush and clear water. Use a "wet and dry" vacuum to remove the water as it accumulates on the floor of the basement. Small amounts of water can also be absorbed with a sponge or towel and wrung into a bucket for removal. Avoid prolonged moisture exposure in the basement to avoid mould growth.
Seal the concrete walls of the basement. Apply the commercial concrete sealer with a brush, roller or sprayer. Allow the sealer to dry according to manufacturer's instructions. Paint the sealed concrete wall, if desired, with standard interior paints.
Remove wall mould
Remove wet porous materials from the basement and dispose of them properly. This includes wet carpeting, wood and plaster wall materials or wet acoustical ceiling material.
Clean non-porous surfaces, such as the cement basement walls themselves, with a mixture of 10 per cent bleach and 90 per cent water. Wear rubber gloves while applying the bleach mixture with a scrub brush or mop. Allow the bleach mix to remain on the walls for at least 10 minutes.
Remove the liquid used during the cleaning process with a "wet and dry" vacuum. Alternatively, use a sponge or towel to absorb the water and wring it into a bucket for removal.
Wear rubber gloves, a respirator and eye protection when working with the bleach water mixture.
Make the 10 per cent bleach solution by adding 250 ml (1 cup) bleach to 4.5 litres (1 gallon) of water.