How to remove mould from walls

  • Killing mould: Scrubbing your walls will help eliminate mould.

    Killing mould: Scrubbing your walls will help eliminate mould.


Mould on your interior walls doesn’t just look unpleasant; it can be a health hazard for your family. Depending on the amount and location, its presence also suggests a larger problem in your house — water infiltration.

For this project, we will focus on solving the mould problem. The remedy is twofold:

1. Control moisture and;

2. Kill the mould. While the former may take a more involved approach depending on the situation, the latter often can be done with some bleach, water and a bit of elbow grease.

Know Your Mould

and Mildew

Mould can grow in your home wherever there’s an abundance of moisture, especially when it’s allowed to remain for extended periods of time. Mould usually appears on walls, ceilings and floors of homes where moisture management is not at its best. In particular, areas such as basements, shower walls and windowsills are areas where mould commonly likes to live. Mould and mildew, for all intents and purposes, are essentially the same thing; mildew is generically used to describe many minor mould problems in the home, such as on shower tile grout. However, some moulds can become highly toxic to people if left to prosper. Mould can cause allergic reactions, asthma and other respiratory complaints and is especially a risk for small children, the elderly and those with existing respiratory illnesses or weakened immune systems.

Control Moisture

According to the US Environmental Protection Agency (EPA), there is no way to eliminate all mould and mould spores indoors. The key to mould control is controlling indoor moisture:

ŸFix Water Problems (leaks, etc)

Fix leaks as soon as you find them. Not only does a leaky basement or roof mean immediate structural damage, if not remedied, the waterlogged areas allow mould to thrive. See the project Repair Basement Leaks. Clean and dry any damp or wet building materials within 24 to 48 hours to prevent mould growth. If you don’t and mould infiltrates them, they will need to be removed to completely fix the mould problem.

ŸReduce Indoor Humidity

The more humid your home is, the more likely it will be a haven for mould spores. Reduce humidity by increasing your home’s ventilation and by keeping air from remaining warm and stagnant. Vent large appliances, such as washer/dryers, as well as your bathroom and kitchen. Use air conditioners and de-humidifiers.

ŸPrevent condensation

Insulate exterior walls, roofs, windows and pipes to reduce the potential for moisture forming from condensation.

Remove Mold from

Basement/Concrete Walls

Step 1. Prepare the Area

You’ll notice mould in your walls by its appearance — usually black, white or bluish patches on your basement walls. It can also grow on any organic material adjacent to the mould-covered areas, such as carpet, cardboard boxes, etc. Remove these affected items from the wall and dispose of what you can. Furniture may be salvaged with a good cleaning, but in some cases it may have to be thrown away. Moving these items out of the way will also give you room to work when removing the mould.

Step 2. Start Scrubbing

To kill mould, there are many commercial products available. Bleach, however, is considered the best thing to kill it, when combined with old-fashioned hard scrubbing. Mix one part bleach with three parts water in a bucket. Using a scrub brush or heavy-duty sponge, vigorously scrub the mould-affected wall with the bleach/water solution until the mould spots have disappeared. In some cases, you may need to let the solution remain on the wall for a few minutes after you’ve applied it to let it soak in. For tough mould-infested areas, you many need to use both a formulated mould remover and a bleach/water solution to get the job done.

Safety Alert!

Ÿ Wear rubber gloves to protect your hands and safety goggles to avoid splashing the bleach solution in your eyes. Also, wear a respirator mask or dust mask to protect yourself from any mould particles that may become airborne. If possible, ventilate the basement while you work. Wear old clothes since you may get some of the bleach on yourself.

After you’ve scrubbed the affected walls, dry them with a towel and check the surface for any mould growth you may have missed. Replace the items you moved back into the basement, but make sure you don’t put back anything with mould on it — you may end up where you started in a few weeks.

There may be some stains on the walls even after you’ve scrubbed them. These can be removed by using a mould/mildew stain remover, available at your local True Value hardware store.

Helpful Tips:

Ÿ Purchase a dehumidifier for your basement to keep the air dry and as inhospitable to mould as possible.

Ÿ Keep an eye out for any leaks in the basement.

If you plan on painting the basement walls, use a stain-blocking primer and paint primer and paint. It may also be necessary to seal your basement with a waterproof sealant before you prime and paint to keep out moisture and mould.

Remove Mould from

Drywall/Painted Walls

Mould can often grow on drywall and painted interior walls, especially in areas where moisture and humidity are a factor, such as kitchens and bathrooms. Walls can also be affected if your roof or exterior walls are infiltrated by water. If the drywall remains wet, mould can begin to grow and penetrate the drywall throughout. When this happens, the drywall must be removed and replaced, as you will not be able to get rid of all mould under these circumstances.

Step 1. Assess the Damage

If you notice mould on any interior walls, assess the condition of the wall and the extent to which the mould has taken over. If the drywall has been compromised, is crumbling or bowed out and covered with black or bluish splotches, it will need to be replaced. If the wall is structurally sound but still covered with mould, you should be able to remove the spots with a cleaner and a bit of scrubbing.

Safety Alert!

Ÿ Some mould is better off remediated by professionals because it may be very toxic when present in large amounts. While unlikely, unless your home has extensive water damage from flooding or some other catastrophe, you probably won’t come across an excessive amount of this kind of mould, commonly referred to as “black mould”. If you do have large amounts throughout an interior area — anywhere around 10 sq. ft. — call a professional to have it removed.

Step 2. Prepare the Area

Because you’ll be using bleach or commercial mould-killing chemicals to remove the mould, you’ll need to protect surrounding surfaces, such as flooring, from any kind of spills that might cause damage. Cover the floor with plastic drop cloths and tape them into place so they don’t move around. It doesn’t hurt to keep some old towels handy to catch any spills.

Step 3. Get Rid of the Mould

The best thing for removing mildew and mould from walls is a bleach/water solution. Mix 1 part bleach to 3 parts water and apply it with a sponge or rag.

Safety Alert!

Ÿ Wear waterproof rubber gloves when cleaning with bleach or other cleaners to protect your hands.

Helpful Tips:

Ÿ In kitchens and bathrooms, tile grout can sometimes develop patches of mildew. You can scrub this away with an old toothbrush. Wash down the walls after you’ve scrubbed.

Step 4. Use a

Stain-Blocking Paint

When you’ve finished cleaning away the splodges of mould, there still may be stains left on wall surfaces. Prime the wall with a stain-blocking primer then paint using paint as a topcoat.

Congratulations, you’re done! Stay vigilant and look for potential signs of mould by keeping in mind where and how it can grow.

Henry Durham is a Director at Gorham’s (441 295-1550).

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Published Apr 4, 2013 at 8:00 am (Updated Apr 3, 2013 at 5:43 pm)

How to remove mould from walls

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