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Mold thrives in any condition subject to humidity (water infiltration, condensation, etc.). They are found on walls, ceilings, windows, floors, insulation and coating of air ducts and, in the basement.

Molds are fungi, invisible to the naked eye, found in nature. They are carried into homes by drafts, humans and pets. To grow, molds need water and nutrients, such as drywall or cardboard. When they grow extensively, molds can cause health problems.

Know how to recognize the presence of mold

Mold is often found in damp and poorly ventilated places.

They can grow all over the house. Some signs indicate the presence of mold or excessive humidity:

  • the presence of spots of various colors, but often greenish or black:
    • on walls, ceilings or carpets,
    • around windows,
    • in wardrobes, etc. ;
  • the presence of a characteristic musty, earthy odor;
  • the presence of dark circles, warping, chipping or other signs of water infiltration on walls or ceilings, which may indicate the presence of a problem hidden behind the materials.

Usually, it is not necessary to have the air or surfaces analyzed to confirm the presence of mold. Indeed, when mold is visible or there are signs indicating its presence, it is rather necessary to conduct a careful inspection of the house to find the cause and take the appropriate measures to correct the situation.

Tips for detecting possible causes

At least once a year, inspect the exterior of the house to make sure everything is in good condition

  • roofing;
  • coating;
  • attic;
  • gutters;
  • sealing of joints;
  • drainage, etc.

Perform regular maintenance on the house as well as a full inspection of all rooms at least once a year. This makes it possible to detect traces of water infiltration and mold:

  • behind the furniture;
  • in wardrobes and storage spaces;
  • in the basement, etc.

Avoid mold growth

Structural mold

Act quickly in the event of water damage.

The presence of stagnant water, seepage or water-soaked material promotes the development of molds.

  • Clean and completely dry any water damage within 24–48 hours. Beyond this period, molds can develop.
  • Discard porous materials heavily damaged by water such as
    • gypsum panels;
    • the rugs;
    • cardboard tiles;
    • insulators;
    • mattresses;
    • upholstered or upholstered furniture, etc.

Avoid having too much humidity in your home.

The regular presence of condensation on windows or walls may indicate that the ambient humidity is too high. To avoid increasing the indoor humidity rate:

  • Limit frequent long showers.
  • Turn on the fans when bathing, showering and cooking food.
  • Make sure the dryer hose is securely connected to an outside outlet.
  • Limit the use of the humidifier and carefully follow the maintenance instructions provided by the manufacturer.
  • Empty and clean the dehumidifier tank regularly. In summer, it is generally recommended to install it in the basement. Follow the instructions provided by the manufacturer to ensure proper operation.
  • Make sure that the humidity in the air in the house is kept low enough to prevent condensation from forming (usually between 30% and 55%). Devices that measure humidity in the house (hygrometers) are
  • inexpensively available at most hardware stores.
  • Avoid storing firewood indoors.

Ventilate adequately

  • Open windows, if necessary, to ventilate the house.
  • Make sure that the air exchanger or other ventilation system is used properly and follows the maintenance instructions.

Eliminate mold.

It is important to identify and correct any cause of water accumulation or infiltration such as a broken pipe, flooding or sewer backup.

Clean affected surfaces without delay and discard damaged porous materials.

For small areas (a window sill, for example):

  • Remove stains with a clean cloth and all-purpose cleaner. The use of bleach is not recommended;
  • Dry the surface well.

If the affected areas are large (over 1 sq m.), numerous, difficult to clean or if the mold has relapsed after cleaning:

  • Call on a specialized company. This will be able to better assess the extent of the work to be undertaken and help you detect and correct the source of the problem;
  • Discard porous and badly water damaged items.

 Attic mold

Help and Resources

For technical advice, consult the documentation from the Canada Mortgage and Housing Corporation (CMHC)  .

Several private firms offer cleaning services. Make sure the selected firm has the skills to research and confirm the cause, location and extent of the problem. Do not hesitate to ask questions about the experience the company has. Air samples are often very difficult to interpret. In the vast majority of cases, they are not needed to assess the problem.


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