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Mould - Tips to mould in your home.

Every house has some degree of mould and bacteria, no matter how clean it looks. What’s important is to keep the number of mould spores in your home low and prevent these germs from thriving in order to protect your health.

Mould overgrowth—especially when reproductive spores are inhaled—triggers respiratory ailments such as hay fever, nasal allergies and asthma, as well as rashes and eczema when it touches the skin. And if ingested, significant concentrations of toxic bacteria can cause abdominal cramping, diarrhea and fever.


  • Hay Fever

  • Nasal allergies

  • Asthma

  • Rashes

  • Eczema

  • Abdominal cramping

  • Diarrhea

  • Fever


How do you know if your home has too much moisture? For one, the indoor environment might seem damp or musty, there can be signs of moisture on walls, on the ceiling, in corners and around windows, plus the windows might have some condensation build-up.

Homeowners can also use a moisture meter or hygrometer, which is a digital device that measures air’s water-vapour content. A home’s relative humidity should be within the 30 to 50 percent relative humidity (RH) range. But if you want to know of your home has a mould issue for sure, it’s best is to hire a pro to look for potential moisture issues around your home and possibly test the air.

Some home inspectors offer Indoor Air Quality (IAQ) assessments. During these assessments a home inspector will go through the entire home and identify potential indoor air quality risks, including moisture issues that can lead to mould. They can also take indoor air samples, which are sent to a certified lab for analysis. They can even give you a mould spore count and send you a report with results.


Mould needs moisture and food to grow, and unfortunately homes provide the perfect environments for these bacteria to thrive.

Mould feeds off of many building materials found in homes, such as paper, wood and carpeting. Walls are made of wood studs and drywall—both of which will grow mould. Because these materials are so prevalent in homes it is difficult to eliminate them entirely. Instead homeowners must control moisture levels to prevent mould growth.


Getting rid of mould-producing

germs and bacteria is impossible

—they’re everywhere. Your best defense against mould is to prevent these spores and bacteria from growing in your home.

To do this, remove excess moisture and humidity from your home through proper ventilation, especially in traditionally damp areas, such as the basement, bathrooms, laundry room and kitchen. You can also prevent moisture from entering your home through weaknesses in the building envelope, such as flashing, caulking, rotted framing around windows, cracks in the foundation or a roof leak.


(less than10 sq.ft.)

If you see surface mould on less than 10 square feet, you can usually handle the clean-up yourself. Here are some tips on doing it right:

  1. Wear rubber gloves.

  2. Use a HEPA filter respirator to reduce the number of mould spores you breathe in, or at the very least a disposable dust mask.

  3. Wear safety goggles and protective clothing that can be discarded.

  4. Turn off your HVAC system to prevent mould spores from spreading.

  5. Remove surface mould by using an antimicrobial solution, like Concrobium Mold Control®.

  6. Work for small intervals and take breaks by breathing in fresh air.

  7. Keep windows open both during and after the clean-up.

  8. Place a fan near a window to blow air out of the room that contains mould.

  9. Cover air return vents in the vicinity tightly.

  10. Double-bag all clean-up materials before removing and disposing them.


  1. Attic

  2. Ceilings, ceiling tiles, as well as in corners

  3. Drywall

  4. Wall cavities

  5. Ductwork

  6. Around windows & windowsills

  7. HVAC systems

  8. Masonry surfaces

  9. Sump pump & drains



Caulk and grout keep water from seeping into critical joints that must remain watertight (e.g. where countertops and backsplashes meet, between tile, around faucets and drains). If it’s dried out, missing or crumbling it can't do its job.

THE FIX: Recaulk and regrout, but always remove old material so the new seal isn’t compromised. Grout isn’t waterproof. It should be treated with a moisture-barrier once it’s newly applied and sprayed with an antimicrobial solution, like Concrobium Mold Control® to prevent future mould growth.


Your kitchen and bathroom need proper ventilation. They are the source for a lot of moisture in your home and this moisture can end up in your walls, floors, ceiling and attic. Exhaust fans pull air from inside your home and pushes it outside. The air shouldn’t be going into the attic, behind a wall, in the ceiling, crawlspace or anywhere else. It should only be going directly outside.

THE FIX: Always run the exhaust fan when cooking or taking a shower and at least 20-30 minutes after. If you don’t have a fan, install one. Also, after showering wipe up excess water and draw the curtain closed so it dries. If relative indoor humidity is consistently high consider investing in a dehumidifier.

TISSUE TEST: If your exhaust fan seems weak, do the tissue test. Turn your exhaust fan on—could be the one in the kitchen or bathroom—and hold a tissue up to it. If the fan holds the tissue it’s probably fine—if not, you might need to replace the fan. If any of your exhausts fail the tissue test bring in an HVAC pro.


Most of a home’s moist air is expelled through the attic due to what’s called the stack effect, which is when warm air rises and is then sucked out of a rooftop opening and replaced by cooler air. When attic ventilation is lacking, humidity accumulates and can cause mould to grow on materials like wood framing, insulation, drywall and paint finishes.

THE FIX: Open gable vents and clear any obstructions from soffit vents. If your attic-vent opening is too small, increase it by asking your contractor to add soffit and ridge vents. The International Residential Code (IRC) calls for a total net-free ventilating area that’s at least 1/150 of the area of the space ventilated for most situations.

  1. Ridge Vent

  2. Gable Vent

  3. Roof Vent

  4. Bathroom Vent

  5. Soffit Vent


Screwed-in strips of flashing (usually rubber or sheet metal), along with roof shingles and siding channel water away from chimneys, vent stacks, dormers, skylights, windows and doors. But if the flashing doesn’t lie flush against a seam, water can seep in underneath leading to mould growth and structural damage.

THE FIX: Take a look at the flashing on your roof after a bad storm to make sure it’s intact. Inspect places where the garage meets the house, where windowsills join siding, and wherever roof lines meet and dip into valleys. If the flashing has become loose contact a professional roofing contractor to inspect your roof and make any necessary repairs.


Even small leaks can lead to mould—and under-sink drain traps, shut-off valves, and underneath toilet tanks are common trouble zones. If the base of a vanity cabinet is saturated or warped you might have a leak in the plumbing or a clog that is causing a leak.

THE FIX: Contact a licensed plumber to tighten the large slip-joint nuts that keep drains clog-free. Stop leaky shutoff valves by backing one off slightly, or gently turning it clockwise if it’s open too wide. Otherwise, call the plumber for a replacement.


  1. Fix leaks in the building envelope as soon as possible.

  2. Look out for condensation, wet spots and signs of moisture.

  3. Insulate or increase air circulation to increase surface temperature.

  4. Increase ventilation (if outside air is cold and dry) or dehumidify (if outdoor air is warm and humid) to reduce the moisture level in the air.

  5. Repair ventilation leaks.

  6. Treat surfaces in potential problem areas with an antimicrobial solution, like Concrobium Mold Control® to prevent mould growth.

  7. Keep heating, ventilation and air-conditioning drip pans clean and unobstructed.

  8. Make sure moisture-generating appliances, like dryers, are venting outdoors, not into the attic, garage or a wall cavity.

  9. Keep up with regular building/HVAC inspections and maintenance.

  10. Keep shrubs and greenery away from foundation walls and make sure the ground is sloping away from the foundation.

  11. Replace bad windows to double or triple pane, with Low E film, argon gas filled glazing and/or with insulating spacers between panes.


  1. Concrobium Mold Control®—a patented, Health Canada and EPA-registered antimicrobial solution that eliminates and prevents mould without the use of harmful chemicals.

  2. PinkWood—a fire- and mould-resistant coating that helps protect wood framing, substrate and sheathing from mould, moisture and rot.

  3. Amdry Insulated Subfloors—an insulated subfloor panel that has a moisture, mould and mildew-resistant surface film, plus raised drainage and air circulation channels. When these subfloor panels are placed below flooring and over concrete, they reduce surface moisture and temperature fluctuations that could lead to mould and mildew growth.

  4. Roxul’s ComfortboardTM IS— stone wool insulation board that is vapour permeable and moisture-resistant. It can be fastened to interior walls on the outside face of the exterior studs of a home, or to the exterior side of the basement foundation. It will not absorb water, making it resistant to mould and mildew, and it’s also vapour-permeable, which allows for fast outward drying during cold weather. This let’s any trapped moisture in wood framing to dry out quickly, even if the framing is wet from construction or becomes wet due to a leak.

  5. Schluter KERDI-BOARD—a waterproof, temperature-resistant and vapour retardant drywall product that can be installed below tiling in areas where moisture is likely to occur, such as in bathrooms and showers.

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