Mould growth can occur in buildings where water has infiltrated areas due to heavy rains, plumbing failures, flooding or high humidity. It is important to report water leaks or water ingress events as soon as possible to help prevent mould growth.



Mould is found in virtually every environment and can be detected both indoors and outdoors, year round. Mould growth is encouraged by warm and humid conditions.

All buildings have a background concentration of settled spores. However, these spores do not pose a hazard until three essential conditions for mould growth are present: a suitable temperature, appropriate substrate and adequate moisture. Mould will colonize on a wide variety of construction materials and building contents including drywall, wood and wood products, ceiling tiles, wallpaper and carpets.

Health effects

Mould can affect the health of building occupants in many ways and is usually caused by the inhalation of the mould spores.
Common symptoms listed by Health Canada include:

  • Eye, nose and throat irritation
  • Coughing and phlegm build-up
  • Wheezing and shortness of breath
  • Symptoms of asthma
  • Allergic reactions

Mould prevention

Since mould requires water to grow, it is important to prevent building moisture issues by reporting any signs of water ingress in a timely manner. This includes:

  • plumbing leaks
  • leaks in the building envelope (e.g. windows, foundation, roof, etc.)
  • condensation on building materials
  • wet spots or water staining
  • musty odours