Mould in your home

Updated September 11, 2023

In cold, damp weather or warm, humid conditions, excess moisture can easily kickstart the growth of mould in your home. Mould can grow in many places: walls, ceilings, carpet, books, and even toys. But worse than that, mould is a health hazard—young children, people with asthma, and seniors are particularly at risk.

This article will look at what mould is, how it forms, how to detect and prevent it, and how to get rid of it. We will also look at some of the health symptoms, and how mould is treated in home insurance.

Mould growing on a wall

What is mould?

Mould (or mildew) is a fungal growth that forms and spreads on damp or decaying organic matter. Mould needs water and nutritive material to grow. Indoors, it can form on drywall or cardboard and outdoors, it forms on fallen leaves. Mould spores are invisible to the naked eye, so it is easy for mould to enter your home via air currents, humans, and pets.

How to detect mould

Mould can form anywhere in your house, you’ll most often encounter it in damp and poorly-ventilated areas. The tell-tale signs of mould are different-coloured spots (often green or black) on walls and ceilings, around windows and in closets. Stains or peeling paint on walls and ceilings can also be a sign of mould, along with an earthy smell in the house.

Health problems caused by mould

Mould can cause a number of symptoms depending on the level of exposure and the health of the individual. Here are some of the most common health symptoms of mould:

  • Irritation of the eyes, nose and throat
  • Runny nose, sinus congestion, and cold-like symptoms
  • Wheezing and coughing
  • Asthma attacks
  • Chronic fatigue and headaches

If you feel that these symptoms were caused by mould, you should contact a health-care professional.

How to prevent mould

There are several simple steps you can take to stop mould from forming in your home.


At least once a year, inspect the outside of your house to make sure there are no signs of mould. Check the roof, siding, attic, gutters, drains, and anywhere else that’s exposed to moisture or where air circulation may be poor. Inside the house, check behind furniture, in closets and storage spaces, and in the basement or crawl space for water infiltration and signs of mould.

Clean water damage

In the event of any water damage in your home, you need to clean and dry the affected area within 24 to 48 hours, since standing water and wet materials can promote mould growth. Throw out any materials that suffer heavy water damage such as drywall, carpet, cardboard tiles, insulation, mattresses, upholstered furniture, etc.

Avoid high humidity

Your home may have high levels of humidity if you see condensation on windows or walls. The humidity level in the house should be between 30% and 55% to prevent condensation. Here are some of the things you can do to avoid high humidity in your home:

  • Take short showers
  • Activate exhaust fans when showering, taking a bath, or cooking
  • Limit the use of humidifiers
  • If you have a dehumidifier, empty and clean the tray regularly and run it in the basement during the summer
  • Do not store firewood indoors
  • Ventilate the house by opening windows and doors
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How to eliminate mould

While you can clean small to medium areas affected by mould (1-3 square metres) on your own, you will need an expert assessment and cleanup for anything bigger than 3 square metres. If you are a tenant and you see mould, inform your landlord.

Vulnerable individuals such as pregnant women, infants, children, seniors, people with asthma, allergies and other health issues, and pets should not be in or around the cleanup area.

You will need the following protective gear:

  • safety glasses or goggles
  • a disposable N95 mask
  • household disposable gloves

You can wipe away mould spots from small areas by using a clean cloth and an all-purpose cleaner. Remember to quickly dry the surface after cleaning. Bleach is not necessary to clean up mould. Don’t forget to dispose of any water-damaged items, like drywall.

If, after cleaning, the mould returns, it is most likely the source of the moisture is still present. In this case you’ll need to seek professional assistance.

Home insurance considerations

Pretty much all home insurance policies exclude coverage for mould damage.

However, an insured event that caused mould would likely be covered. For example, if the water from a burst hot water tank caused mould to form on drywall, the mould cleanup would typically be covered as long as the policy covers the loss.

On the other hand, mould that forms due to negligence (for example, from high humidity, lack of ventilation, or allowing the accumulation of standing water) would not be covered because that is something the homeowner can and should prevent.

Commonly asked questions

Can I test the air in my home for mould?

Health Canada does not recommend testing the air for mould. Air tests do not provide health information and do not reveal the cause of mould damage. While a test will detect mould spores in the air, they are a natural part of the environment, and their presence does not necessarily mean there is a problem.

Can I just paint over mould on a wall?

Painting over the mould will not remove the mould. The mould will continue to grow under the paint, causing the paint to peel. You have to remove the source of the mould.

Can I use an air purifier or air filter to remove mould?

While an air purifier cleans the air, it will not eliminate mould. You will still have to remove the source of mould growth. An air filter removes a percentage of the mould spores, but the remaining spores will settle on the floor and recirculate throughout your home.

Want to learn more? Visit our Home and Personal Safety resource centre to find more information about protecting your family and your home. Or, get an online quote in under 5 minutes and find out how affordable personalized home insurance can be.


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