July 22, 2005

Residential

Stage set for mould infestation

Building boom could lead to ‘leaky condo’ syndrome

PEGGY HILL

staff writer

The current residential building boom could be laying the groundwork for a future rise in mould contamination, says an expert with the Canada Mortgage and Housing Corporation.

Mark Salerno, CMHC’s district manager for Greater Toronto Area, said the hot housing sector is reminiscent of the building boom in Vancouver that occurred after Expo ’86. After a cyclical downturn, the industry had lost workers, but then the boom came, and with it a shortage of skilled labour.

That was followed by the B.C. leaky condo crisis.

Mark Salerno

“If what we’ve seen in the past is an indicator, it’s quite possible that there will be some building failure issues” in Ontario.

However, he said a positive outcome of the leaky condos is that the use of rainscreen wall protection is becoming more common in residential construction.

Features of the rainscreen assembly include channels inside the cladding that allow water to drain out. Another is pressure equalization. The cavity inside the cladding contains the same air pressure as outside the cladding so that the water will drop and drain instead of being pushed farther in.

Salerno said the technology has been employed in commercial buildings for 15 to 20 years. It is also a standard part of brick veneer construction. He said the cavity is now commonly created with other materials, such as vinyl siding, stucco, or wood.

According to Salerno, the key to avoiding mould infestations is recognizing that moisture management is a shared responsibility of designers, contractors, and building operators. Each must be educated and aware of the moisture management strategies within their domains, and also look at areas of shared responsibility, where one impacts the other.

“If designers are designing buildings that inherently do not properly manage the moisture, or they haven’t provided adequate detailing of key junctions, then how is the builder supposed to rectify that. So that’s an area of shared responsibility.”

Taller, multi-residential buildings are at higher risk for water penetration because of greater wall exposure to wind-driven rainwater. However, Salerno noted the building envelopes of more energy-efficient condominiums will have greater rigour and said it’s very positive that some buildings are looking into rainwater management strategies.

Buildings with continuous ventilation could also reduce or avoid the growth of mould, he said.

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