Studies in B.C. test rainscreen stucco cladding systems

Canada Mortgage and Housing Corporation has been testing rainscreen stucco systems to see how well they withstand large earthquakes.
Following the leaky-condo crisis and problems with moisture penetration on residential buildings in B.C., many authorities in the province have mandated the use of rainscreen stucco wall systems. These systems have an air cavity incorporated behind the cladding to allow bulk water to drain away immediately behind.
TBG Seismic Consultants and the Department of Civil Engineering at the University of B.C. did the research. They compared rainscreen and non-rainscreen stucco systems, doing static and dynamic tests on 18 panels, each measuring (4 x 8 ft. (1,219 mm long x 2,438 mm high), with 2 x 4 in. wood studs at 16-in. centres. The base sheathing was 0.4-in. thick oriented strand board. The full scale dynamic tests were done to simulate the Kobe and other earthquakes on houses of approximately 1,000 s.f. (93 m2).
The research, reported in December 2003, showed that the performance of rainscreen and non-rainscreen systems are comparable and that both have the potential to eliminate major structural earthquake damage in residential wood frame buildings, single family and multiple-unit.
However, to enhance the systems’ performance, the researchers recommended that plywood strapping secured with roofing nails should be used with rainscreen stucco construction. It also said that the use of 2-in. (50 mm) staples as lath fasteners should replace the current practice of using nails in these systems.
CMHC has also recently reported on research into the water penetration resistance of windows. Research consultant on that project — reported in November 2003 — was RDH Building Engineering of Vancouver.
See.cmhc.ca