Finding and Dealing
With Mould in the
Home
Introduction
Mould naturally grows in our environment. More than 1000 different species of mould live
and grow in the air, water and soil around us, and can easily and quickly grow inside our
homes, where we do not want it to be. Unwanted mould can grow within 2 to 3 days.
Some mould can also be harmful to our health, producing toxins that may make humans
or animals sick. Keeping our homes healthy can be impacted by how well prepared we
are to look for and deal with mould issues.
This resource has been developed to help people and agencies to find and deal with
mould in residential homes.
This resource does not differentiate between mould, mildew or other dark staining that
may be found in the home. It can be difficult to tell the difference. If you think it might be
mould, we recommend that you treat it as mould
Mould Risk Levels
Knowing the risk level of mould issues helps to understand how best to deal with the
issue. Here is a general guideline to understand the three different levels of growth may
be:
Minor Concerns:
Looking at potential surface mould (or mould that you can see), areas that are less than
10 square feet are considered to be minor and may be dealt with by cleaning the area
with a mould control product
Moderate Concerns:
Area of mould that cover up to 30 square feet collectively (a sheet of drywall is 32 square
feet), or mould issues that are deeper than surface level usually require removal of
material. If you are not comfortable with the type of work initiate a maintenance work
order. Mould related to water leaks may fall in this category.
Significant Concerns:
When mould issues grow beyond 30 square feet or look like they are widespread (like
along an entire wall), or if mould is found around heating / ventilation systems, concerns
may be more significant. In these cases initiate a maintenance work order. When
significant concerns are found, they may impact your health and wellness.
What to Look for
Mould can sometimes be tricky to find. However, there are some general indicator’s that
there may be mould growing in your home:
MUSTY SMELLS
As you walk around the house check the air for
any trace of mould odor, especially in the
basement. Mould is often times hard to spot and
mould spores are invisible to the naked eye so a
musty smell is often a good indicator of a problem.
PATCHES OR STAINS ON THE
CEILING
Often times you will find patches of
discolouration or stains. These typically found
on the ceilings, in the bathroom or in the
corners by windows and exterior walls.
WINDOWS
In colder climates we will often find mould growth on
the windows due to condensation and lack of
ventilation. The mould here is feeding on the dust
and can easily be cleaned. The moisture from the
condensation must be corrected to ensure mould
does not return or spread to other areas.
Common Concerns
In Corners Under the Kitchen Sink
Mould may grow on ceilings and Mould may grow under kitchen
around baseboards, especially in sinks, since there is a lot of water
corners, where there is limited air and the caulking around skinks
flow. (to make them waterproof) can
wear over time.
Mould may grow behind furniture Mould may grow on concrete
since furniture blocks the air flow. walls in basements because
Make sure to move and look water may easily condense on
behind furniture when you look colder walls in warmer homes.
for mould.
Process and Products for Cleaning Mould
1. Recommended product is Swish ES64-4 General Purpose Neutral Disinfectant.
Ensure you follow product directions and wear the recommended Personal Protective
Equipment (PPE).
2. Dilute the ES64-4 at 16ml per litre of water
3. Soak the affected area with the diluted ES64-4 Enviro Solutions ES64 General
Purpose Neutral Disinfectant, 4.73L
4. Remove gross filth and heavy soil deposits (visible mold or mildew)
5. Completely soak the entire affected area with a mop, sponge, cloth or sprayed on
diluted ES64-4
6. Allow to air dry
7. Repeat weekly or when growth re appears.
Exterior (Outside) Home
Wooden Soffit
Mould can form on the exterior components of a home.
While it is not normally a health issue (after all, mould spores occur naturally
in the air), when significant mould appears on the soffit, it should be dealt with
to prevent spread and further contamination.
This is more common on the side of the house facing away from the sun, it
does not get the opportunity to dry completely which can lead to the formation
of mould.
Tips for Moisture
Actions that will help to reduce humidity:
Vent appliances that produce moisture, such as clothes dryers and
stoves to the outside where possible. (Gas fired appliances such as
stoves or heaters produce water vapor and will increase the humidity
unless vented to the outside.)
Use air conditioners and/or de-humidifiers when needed.
Run the bathroom fan or open the window when and after showering.
Use exhaust fans or open windows whenever cooking, running the
dishwasher or dishwashing, etc.
Actions that will help prevent condensation:
Reduce the humidity.
Increase ventilation or air movement by opening doors and/or windows,
when practical. Use fans as needed.
Cover cold surfaces, such as cold water pipes, with insulation.
Maintain an appropriate and consistent indoor air temperature.
Moisture Control is Key
When water leaks or spills occur indoors – act quickly. If wet or damp
materials or areas are dried 24-48 hours after a leak or spill happens, in
most cases mould will not grow.
Clean and repair roof gutters regularly.
Make sure the ground slopes away from the building foundation, so that
water does not enter or collect around the foundation.
Keep air conditioning drip pans clean and the drain lines unobstructed
and flowing properly.
Keep indoor humidity low. If possible, keep indoor humidity below 60
percent (ideally between 30 and 50 percent) relative humidity. Relative
Humidity can be measured with a moisture or humidity meter, a small
instrument available at many hardware stores.
If you see condensation or moisture collecting on windows, walls or
pipes act quickly to dry the wet surface and reduce the moisture/water
source.
Do not store items or place storage shelves closer than 12inches from
walls
Store items on pallets or shelves to promote air flow
Condensation can be a sign of high humidity.
References and Resources
For more information:
Mould, Dampness and Humidity
https://www.canada.ca/en/health-canada/services/air-quality/
indoor-air-contaminants/reduce-hmidity-moisture-mould.html
Mould and your Health
https://www.canada.ca/en/indigenous-services-canada/services/
firs-nations-inuit-health/health-promotion/environmental-public-
health/environmental-health/your-health-at-home/mould.html
Measuring humidity in your home
http://publication.gc.ca/collections/collection_2011/schl-cmhc/
nh18-24/NH18-24-1-2009-eng.pdf
The importance of bathroom and kitchen fans
http://publications.gc.ca/collections/Collection/NH18-24-17E.pdf
The basics: protect your home and family
https://www.canada.ca/en/health-canada/services/home-garden-
safety/basics-protect-your-home-family.html
Hazard-Check Virtual hours tour
http://www.healthycanadians.gc.ca/healthy-living-vie-saine/
environment-environnement/home-maison/interactive-interactif-
eng.php
