Mold Prevention

Seven steps for getting rid of mold for good


Article and photos by Steve Maxwell

Mold is an essential and healthy part of any natural ecosystem, but when mold appears inside your home, that’s another matter. Mold growing inside any part of your house is ugly, unhealthy and surprisingly common. That’s why every homeowner should understand basic indoor mold control know-how. Here are the six steps you need for effectively dealing with the mold in your life and making sure it doesn’t come back.

Step#1: Assess the Situation

Begin by revealing the full extent of mold growth in the affected area. This could be easy or difficult depending on how much wall, carpet or ceiling you need to tear away. That said, investigation is a step that’s significant for more than obvious reasons.

Mold authorities in Canada and the U.S. say that homeowners can tackle indoor mold issues themselves, but only if the affected area is no larger than 30 or 40 square feet.

Anything bigger is probably a job for a pro. Professional help is also strongly recommended if your situation involves sewage backup. Bacterial contamination poses its own threats that go beyond mold hazards.

Step#2: Eliminate the Moisture Source

Mold is always associated with moisture in some way. Without moisture, mold can’t grow on anything. With sufficient moisture mold can grow almost anywhere. This is why a permanent mold solution always involves creating dry conditions. Liquid water leaks are easy enough to spot, but moisture vapour and condensation can also be a hidden source of trouble. Basements are especially susceptible to water vapour infiltration through masonry walls and floors, and ventilation is not always the answer. See Musty Basement Management to understand when to open windows and when to keep them shut.

Step#3: Make Removal Decisions

Some moldy surfaces are ideal for treatment and restoration, while it’s easier to remove and replace others. Drywall, ceiling tiles, carpet and other non-structural materials should usually be removed, bagged and discarded. Wear a HEPA-rated respirator when removing moldy materials because mold spores will become airborne. Structural and otherwise costly-to-replace areas can be treated.

One often-overlooked source of mold contamination comes from the common practice of storing cardboard boxes on basement floors. Even seemingly dry basements can allow enough moisture vapour to migrate up through the concrete to trigger mold growth on cardboard. That’s why you should never store anything organic directly on a concrete basement floor.

Step#4: Dry the Area

After eliminating the source of moisture, you may still have wet conditions that can lead to trouble. It is essential to create dry conditions before mold treatment can succeed. Air circulation, heat and a dehumidifier are the three most powerful drying tools. You’ll get best results if you monitor the relative humidity of the air in the space with a hygrometer, allowing more or less outside ventilation to speed drying, depending on outdoor temperature and humidity conditions.

Step#5: Kill Mold and Discourage Re-growth

This is where common practice is actually a mistake. While bleach is an acceptable way to kill mold on hard, non-porous surfaces, it can’t do a good job on surfaces that are even a little bit porous. Roots are the reason why. All molds send root-like structures called hyphae into porous surfaces to gather nutrients, and surface tension prevents traditional bleach and water solutions from penetrating deeply enough into wood or concrete to kill the hyphae. Bleach will cause a superficial mold kill in situations like these, but the mold remains established below the surface, ready to return with a vengeance. Also, as toxic as bleach is at first, it actually offers no residual protection when new mold growth starts because it dissipates as a gas.

This is why there are alternatives that are better than bleach when it comes to breaking the mold cycle. Non-bleach products sold as fungicides that carry Health Canada registration have been proven to work by independent testing, and this designation is something you should look for when choosing anything to kill mold. An effective product is Concrobium Mold Control. It’s a liquid that kills mold and mold spores by mechanical action, physically crushing all parts of the mold organism as it dries. This mechanical action explains why a non-toxic product can still kill mold and prevent re-growth if the area occasionally does become moist again. The product remains in place too, providing residual action to kill mold.

Step#6: Prevent Mold Re-growth

Even registered fungicides that offer residual mold control aren’t magic. Ultimately you need to keep moisture levels down to eliminate an eventual mold relapse, and this means different things in different situations. Ensure sufficient ventilation to keep indoor relative humidity at or below 50 per cent during winter, and constantly be on the lookout for roof leaks, water coming in the basement or chronically leaking taps or pipes, especially in hidden places like behind the washing machine or under a kitchen counter.

Not all molds are harmful, but how can you tell the dangerous from the innocent? This is why controlling mold is an important homeowner skill that’s as much about household management as it is about what products to use to kill mold. Keep things dry, remove mold food sources, then understand how to treat areas properly if mold ever does show up. Your home will look better and you’ll be healthier.

Outdoor Mold

Indoor mold is a visual and health issue, but outdoor mold is all about how something looks. Mold can grow on wood decks, composite decks, siding, eaves and just about anything else. Here’s how to clean up mold staining outdoors and prevent it from coming back.

Remove dirt, leaves, twigs, mats and anything else that might give mold shelter from the fungicide you’re using. Treat the area with a yard-safe mold stain cleaner. Concrobium makes one of the only bleach-free, non-toxic house and deck wash products for external mold applications. It comes in a spray bottle for connecting to a garden hose and dousing large areas. It’s won’t harm plants, lawns, pets or anything else it comes in contact with.

Remove persistent stains that remain after initial wash.
Eliminate nutrients. Although you can’t always keep outdoor surfaces dry enough to discourage mold on the moisture front, you can do everything possible to reduce the surface nutrients that are also essential for mold growth. Sweep leaves and grass clippings off your deck or verandah, and keep exterior wall surfaces free of cobwebs, bird droppings and anything organic.

Remove Mold Stains

It’s one thing to kill mold, but it’s another thing to remove stains left by mold. Traditional treatments for removing mold stains include chlorine bleach, hydrogen peroxide or oxalic acid, and while these options do reduce or eliminate staining, they also bleach surfaces and make them uniformly light. In tests I’ve conducted, Concrobium Mold Stain Eraser gets rid of mold staining without scrubbing, and it doesn’t bleach underlying surfaces.

Musty Basement Insights

While it’s true that fresh, outdoor air can be a powerful cure for mustiness and mold, it can also be a powerful cause of trouble. It all depends on the temperature and humidity of outdoor conditions compared with your inside space. This most often becomes an issue with cool basements in summer. When hot, humid outdoor air is allowed to enter a basement, the air cools down, and it loses some of its ability to hold moisture as it does. This is why opening basement windows in summer always causes relative humidity to rise in a cool basement, not drop. Ventilating your basement is a good idea when outdoor temperature and relative humidity is the same or lower than your basement space.

Eliminating Window Mold

Window frames are the most likely place you’ll see mold in your home, and that’s because of our cold Canadian climate. As interior glass surfaces become cold in winter, they trigger condensation of moisture from the warm, indoor air. Anything more than a little moisture on window frames will lead to the growth of black and grey mold, even on synthetic window frames. Removing this mold is simple and easy, and using the right fungicide will also prevent mold re-growth to an extent. The long-term fix is to reduce household humidity levels during winter, and you can’t beat a heat recovery ventilator (HRV) for making this happen. Manufactured by a handful of different companies, HRVs draw fresh outdoor air inside, while exhausting stale, moist indoor air outside. Most of the heat from this indoor air is retained, so it’s more efficient than just opening a window. Dehumidifiers can’t reduce wintertime humidity levels enough to prevent window condensation, so an HRV is the ideal way to control window moisture in today’s tighter homes.