Toronto, Canada – When extensive flooding caused a state of emergency in Peterborough last July, it left thousands of wet basements and damaged possessions in its wake.
It also created a fertile breeding ground for mould, which can foster wood rot, create structural damage and cause serious health problems.
Many of the 2,000 homes assessed afterwards for damage had mould growth, says Trent Gervais, Peterborough deputy fire chief and community emergency planning coordinator. He says the most effective way to deal with mould is to remove it, and that means disposing of affected drywall, wood framing and carpeting.
Christine Bailey, owner of Winmar, a Peterborough company which provides emergency cleanup and restoration work, says mould can be an issue in any home that has too much moisture. Newer homes are often at risk because many are built so airtight that moisture can’t escape.
A hygrometer, which costs from $5 to $20 at hardware or home supply stores, is handy to measure relative humidity in the home, which should be under 45 per cent in the winter, according to Canada Mortgage and Housing Corp.
“If you can control the moisture in your house, you shouldn’t have a mould problem,” Bailey says. “This means having a proper vent and exhaust fan in the bathroom and running it while you shower and for a few minutes afterward. Cooking creates a lot of moisture, so use the exhaust fan over the stove. Mould is everywhere. You can’t eliminate it, but you want the mould count indoors to be less than it is outdoors.”
It’s important to keep your basement dry, which can usually be achieved by using a dehumidifier.
Bailey recommends frequent checking and cleaning of humidifiers mounted on furnaces. One common misconception is that bleach will kill mould.
“I tell people that mould is like a dandelion,” says Bailey. “Even after it dies, the spores can become airborne. And mould is a lot like dead grass – as soon as it gets wet again, it comes back to life.”
Topical mould, such as that on windowsills or on bathroom grout, is not serious and can be cleaned by the homeowner. Wear a mask, safety glasses and rubber gloves and use a solution of water and liquid detergent or vinegar.
According to CMHC, you should seek professional help if there is a lot of mould in your house (extensive growth would be a patch of mould bigger than a sheet of plywood). Also seek help if your home is very damp, if mould recurs after repeated cleaning, or if a family member’s asthma or allergies get worse.
Because mould often grows where it can’t be seen, often the only way to determine if it is present is to have an indoor air quality inspection. Contact your local CMHC office for a list of qualified investigators.