CMHC Report "Molds in Finished Basements"

(Canada Mortgage and Housing Corporation, Canada's National Housing Agency), conducted a survey of 405 houses in the Ottawa region of Ontario, Canada. The objective of the survey was "to determine whether typical 'finished' basements are contributing to poor indoor air quality as a result of mold growth in the finishing materials". About half of the 405 houses "had signs of moisture in the basement". The study then selected 22 for further investigation. Molds were found in 18 of the 22 houses, or 82%. Mold samples were taken from 16 of the 18 houses.

In 100% of those houses, "molds with properties that are harmful to humans were found."

The study concluded:

1. "Some finished basements do present health hazards to the occupants due to the presence of toxigenic and dangerous molds in the wall cavities"
2. "The causes of mold growth in finished basements are directly related to chronic wetting incidents rather than the wall finishing and insulating techniques"
3. "The main chronic moisture sources associated with mold growth in finished basements are exterior moisture sources and wetting mechanisms"

Click here to read the full report.

Rising Damp

Rising damp is the wicking of water through the footing, into the concrete wall, and its evaporation inside the building. Rising damp increases the relative humidity on the inside face of the concrete which leads to mold growth as reported in the CMHC report.

Rising damp does not produce pools of water (as with liquid water entering a concrete wall), but rather a chronic musty smell, growing insidiously stronger when the footing is exposed to more moisture.

The worst case of rising damp occurs when water ponding occurs at the footing level. This occurs over impervious soils where the excavation is inadequately sloped, the drain tiles are not located below the bottom of the footing, and no sub-footing drainage layer was installed.

Even without water ponding, rising damp ccurs when unprotected footings are exposed to damp ground. 'Hygroscopic' concrete wicks ground moisture up into the foundation concrete which is then evaporated inside the building. Fastfoot® prevents this wicking from occurring, providing a drier and healthier indoor environment.

Click here for the use of Fastfoot® to prevent rising damp.

Chris Mattock, Habitat Design & Consulting Ltd.

Chris Mattock, Principal Consultant with Habitat Design & Consulting, sees substantial benefits in footing membranes:

"It makes no sense that builders spend time and money damp proofing the exterior of their foundations walls, yet leave the concrete footings standing in a pool of water. As water vapour always travels from high to low humidity, ultimately this moisture will get drawn inside the building."