The design and construction of multi-family buildings in the Lower Mainland of British
Columbia has come under increasing scrutiny due to the high incidence of water ingress and
resulting decay of materials in the exterior assemblies of these buildings. Most new buildings
and many of the remediated moisture damaged buildings are being built using “rainscreen” wall assemblies, on the premise that that these assemblies are more tolerant of moisture and will limit wetting to levels which can be accommodated by the building materials. Unfortunately, very little data is available to determine how these assemblies actually perform in service. As an industry, we require data on how the “rainscreen” wall assemblies, as currently being designed and constructed, will perform on a long-term basis. Better knowledge of rainscreen wall performance in service will also help identify opportunities for fine-tuning rainscreen assembly design to make them more cost effective and durable.
This article outlines the monitoring systems used in the study. Portions of the results are
presented that relate to anomalies of interest such as, the effect of overhang on wetting, the
results of unexpected moisture levels in the buildings, a comparison of the different cladding
systems used in the study, and a comparison of actual wind and driving rain conditions compared with current design guidelines.
At the time this article was written, the monitoring program was approximately 60% complete. Building 5 had not come online yet due to construction delays and only limited data has been obtained from Building 4. As such, this article does not include analysis of the results from these buildings.
The monitoring project was funded by the Homeowner Protection Office, BC Housing, and the Canadian Mortgage and Housing Corporation.