Patches of mould and mildew are a common problem in bathrooms, basements and other areas where damp and condensation are combined with a lack of ventilation. Not only do these patches look unsightly, but they can also cause medical problems if left untreated. Simply painting over patches of mould and mildew might hide the marks for a while, but unless the mould spores are killed, it is unlikely that will be the last you see of them. Here is a complete guide to killing the mould spores and then covering the stains on your walls. If you only need to cover stains left by damp, our Guide to Covering Damp Stains should help.
Killing Mould Spores
There are numerous chemical mould and mildew sprays available, varying in strength and effectiveness. These are widely available from supermarkets, DIY stores and specialist suppliers. The usage instructions will certainly vary between products, so make sure that you follow them carefully. Some of these chemicals are pretty nasty, so make sure that gloves and eye protection are worn when using them. You must also make sure that there is adequate ventilation in the room before use.
Using Household Bleach
A mixture of 1 cup of bleach diluted in 1 litre of water is a very effective treatment for mould and mildew. Wearing gloves and eye protection, and with windows open, wipe down the wall liberally with the bleach solution. Wipe the wall immediately surrounding the effected area as well. Leave the solution on the wall for about an hour and then rinse off with a clean cloth and warm soapy water. If possible, introduce some heat to the room (portable heater or dehumidifier) to dry the wall and help prevent any missed spores from growing.
Warning: Ammonia can also be used to kill mould spores if you have access to some. Never mix chlorine bleach and ammonia to make a mould treatment. Mixing bleach and ammonia will create very dangerous fumes that could make you seriously ill or even kill you! So, again, NEVER mix chlorine bleach and ammonia.
Natural Mould Treatments
If you want to treat the mould spores in a more natural and eco-friendly way, there are several very good options available to you.
Tea Tree Oil
This is a very cheap and effective way to kill mould spores and help prevent their return. Tea Tree oil will, even when diluted in water, kill up to 100% of mould spores it comes into contact with. It does smell quite strongly (although not an unpleasant smell) but this will dissipate in a few days. To make a Tea Tree oil treatment, mix up 2 tsp of concentrated oil with 2 cups of water. Combine the mixture in a spray bottle, shake well and spray on to the effected areas of the wall. Leave this for a day or two and then wipe down the wall with warm, soapy water.
Another very effective natural mould treatment is white vinegar. White vinegar will kill around 85% of the different types of mould. Although there is an obvious smell problem with using vinegar, it will only last for a few days. As with tea tree oil, white vinegar can be diluted (2 tsp to 1 cup of water) or can simply be sprayed onto the effected areas undiluted. This should then be left for a day and then wiped off with warm, soapy water.
Covering Mould Stains
Before you begin to try to cover the black stains left by mould, you must ensure that you have killed any spores on the surface of the wall using one of the methods above. When the mould has been treated, make sure that the wall is washed down thoroughly or the treatment you used could affect the integrity of any wall covering you apply.
The best way to cover mould stains is to paint over the effected area. Rather than just using ordinary emulsion, it is best to invest in some fungicidal paint. This is specially formulated to help prevent mould and mildew from growing (although it won’t stop mould growing in very damp, poorly ventilated conditions). You can buy fungicidal paint in small quantities if you just want to treat a small patch of wall. You can also buy anti-mould paint designed to be used over the whole room. This is usually more expensive than ordinary emulsion, but really can help to prevent mould returning to a room.
If you plan to wallpaper a wall where mould has been a problem, you should use wallpaper paste that includes a fungicidal treatment. Ideally, paint the effected areas of the wall with anti-mould paint before you wallpaper over it.
Preventing Mould and Mildew
In many cases, mould and mildew are simply a symptom of a damp and badly ventilated room. If mould is very localised (one small patch of one wall for example) check to make sure that there is not a localised cause such as a leaking gutter, pipe or drain. If there is an external source of dampness, this should obviously be fixed before you start to treat the mould.
Rooms that regularly get damp, either through condensation or other means, are prone to having problems with mould and mildew. The easiest way to avoid mould taking hold in rooms that are damp is to improve the ventilation. If possible, open a window at least once a day, for about an hour. If the room is a bathroom, ensure that a window is opened after the shower or bath is used. If you are worried about security, you could instead fit an extractor fan or a ventilator fan.
If a room is cold as well as damp, consider introducing a heater to the room. This could be a portable storage heater, or it could mean adding a radiator (or replacing the existing radiator with a larger one).