pic for mould webBy Matthew Brewer

The weather is a constant source of conversation in Canada and a bone of contention.  Every spring we see flooding occur across the country.  The Prairies encounter flooding frequently during the spring and every fall, Eastern Canada gets hammered with tropical storms and hurricanes.  After all of these events we have to deal with the after-effects: mould.

Mould is everywhere.  The small spores are floating in the air you’re breathing even as you read this.  It’s a ubiquitous part of nature.  These microscopic spores float through the air, landing on surfaces.  If the conditions are not favourable for growth, nothing happens.  But when they land on a surface with the right conditions – dampness and a suitable food source, such as wood or other organic material – a problem will soon occur.

When a spore lands on a suitable surface it begins to grow roots, stem and finally a head, which produces many spores in as little as 12 hours, given the right conditions.  These spores are caught by air currents and can then spread.

The spores are small – a typical mould spore is only around three to 40 microns in diameter.  To understand just how small this is, consider that human hairs measure between 30 and 120 microns in diameter.

Spores can travel very easily, seeking new places to grow.  Sometimes they travel throughout a building using the ventilation system or natural air movement and spread, settling on surfaces, waiting for the opportunity to grow.  Others don’t travel far, if the air movement isn’t favourable.  In these cases, you can have large colonies growing in a relatively confined area in a short period of time.  Each plant produces many spores, which create more growth, which creates more spores…and it goes on until either the food is gone or the conditions change.

Mould causes various issues, both for the building and for the occupants. It uses the building structure as food, which can cause staining or structural damage.  The odours of mould growth can become quite unpleasant – the smell is usually a good indicator of when there is a problem.  Simply put: if you see or smell mould, you have mould.

In recent years the term “black mould” has permeated the media and society.  When I did building assessments, I would often be asked if the mould that was present was black mould.  My reply has often been, “If it isn’t black mould, would you still want it?”  In building structures, no mould growth should be considered acceptable, no matter the colour.  While stachybotrys is black and one of the types with greater recognized risks, having any visible mould is a clear indication that a problem condition exists and should be fixed.

When our health is brought into the picture, things get even more challenging.  Some people have sensitivities to mould and can react from the toxins given off by some types – even mould that has died.  The spores of some types of mould can cause allergic responses in more sensitive people, including those with bronchitis, asthma and other respiratory conditions.  If viable (live) mould is airborne and inhaled by occupants with compromised immune systems, those people can be at increased risk from life-threatening infections.   In general, most of the population only notices the odours from mould growth and takes issue with the esthetic aspect.

How do we prevent it from growing?  The simplest method is to keep it from entering in the first place.  Barring that, the next step is to remove the moisture from the area.  When flooding or water infiltration occurs, it’s key to get the water removed as quickly as possible.  The longer the moisture sets, the further it can penetrate, making removal more difficult and giving mould a better chance to take hold and create more damage.

When significant growth or water infiltration is suspected, it is strongly recommended that a qualified consultant be brought in.  An experienced consultant can determine where the moisture may be coming into the building, as well as find both visible and hidden areas of growth.

If mould has been allowed to grow, how do you get it out?  After the moisture source has been found and removed, cleaning should be determined based on the size of the area.  If it is a small area, less than 1 m2 (10 square feet), it can often be scrubbed with household cleaners, if it is only a surface growth.  Simple cleaning products such as trisodium phosphate (TSP) can be purchased at many stores, or other mould-specific cleaning products can also be used.  While bleach is often used, it isn’t recommended due to the damage that the mould can do to the underlying material, as well as the potential for reacting with any toxins and respiratory risks to the users.

If it appears that the mould is thick, has exceeded one square meter or has compromised the material, it is strongly suggested that a professional mould remediation company do the work. It can quickly become a large project requiring specialized equipment and training.

The remediation crew brought in to clean should be expected to follow industry guidelines.  A valuable resource is the Canadian construction industry’s publication CCA-82, Mould guidelines for the Canadian construction industry.  It offers professionals with information that can be used to do professional cleaning.  Another resource is the Institute of Inspection, Cleaning and Restoration Certification (IICRC).

For many property maintenance or other professionals who may encounter mould, having an awareness course is always beneficial.  These courses are readily available across Canada, and also are available online.

Matthew Brewer is an occupational hygienist.  He offers online awareness training in hazardous building materials, such as mould, asbestos and lead through his company, Hazman Environmental Training Services.  www.hazmantraining.com


  1. Ensure that the source is found prior to closing up a mould area. I hired a professional remediating company after trying to solve the problem on my own. A year later they were back and removed the mould again (at their cost as they never discovered the source the last time) and left me with another contractor to source the problem who didn’t care if it was found or not and the original contractor never followed up. I ended up having to hire two other contractors to find the source to the problem. Very disappointing.

    • imagine the hidden lingering mould that will fester and grow within the hidden areas below and above the high water marks (that were not uncovered during remediation) of the flooded homes in Calgary and High River Alberta.

      Whilst working as an inspector/conciliator with the Ontario New Home Warranty Program (now TARION Corp) 1987-1992, I routinely had to deal with mould warranty problems within new homes due to leaky shower stall and/or bath tub enclosures. The builder would perform minimal remedial work, to no avail. I would be called in, and I would order all drywall etc. to be removed in all directions within five feet of the affected areas, for starters, thus revealing what was unseen behind said wall sheathing. Black masses of healthy growing mould covering framing and the backsides of opposite drywall sheathing on the adjoining rooms’ walls usually greeted the eyes of all onlookers.

      The Calgary/High River homes that have been flooded above the underside of first-floor floor joist heights should be bulldozed.

      The provincial government should pay for same.

      The local municipal governments should be sued by the affected homeowners for damages flowing from the negligent issuance of building permits upon known flood plains, which were just as severely flooded in 1930.

      The provincial government should assist affected displaced homeowners with long-term affordable mortgages in order that they may purchase and/or build new homes on higher ground.

      The remaining homes should be checked for mould growth (via cameras inserted into wall cavities through pre-cut access holes/panels) every six months for the next two years, at government expense.

      Homeowners not wanting to live in their flooded out homes again should get together, arrange for other accommodations, and hold a one-day on-flood- plain-site communal walk-away media event, thereafter depositing their door-lock keys with the lenders, concurrently, en masse.

      Mould is not something innocents (spouses, children and other family members of riverboat real-estate- gamblers who buy residential properties on known flood plains) should have to live with when same has been imposed upon them by the fallout of bureaucratic negligence in league with predictable natural phenonmena.

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