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Stucco, if applied correctly, has the potential to almost eliminate major earthquake damage.
That was one of the major findings of a $1.4 million research project called Earthquake 99.
Dr. Graham Taylor, a structural engineer and owner of TBG Seismic Consultants, in collaboration with the University of B.C.'s Earthquake Engineering Research Facility found that minor changes to the typical exterior stucco finish significantly improved the earthquake performance of wood frame houses.
The two year research project originally arose out of a concern over how wood frame housing (single family, condominiums, and townhouses) was being built without being specifically engineered for earthquakes.
The objective was to test the vulnerability of wood frame buildings and to mitigate risk by developing software that enables design professionals to estimate earthquake damage.
"There is part of the building code, it's like a loophole called Part 9, that says buildings not particularly large don't have to be designed specifically for earthquakes. B.C. housing falls into the category of Part 9 and that struck me as something fundamentally wrong because of the possible vulnerability to earthquake damage," says Taylor, noting that this project was the first of only two to conduct earthquake engineering testing on wood frame houses.
Dynamic testing was conducted on a full scale 1,000 square foot, two storey single family house with 12,000 pounds of concrete block on the roof to represent a clay tile roof. The model was built inside the U.B.C. lab on a special steel frame that was fitted with rollers that could be pushed back and forth by a large jack to imitate the shaking of an earthquake.
While the research focused on B.C. construction, the methodology and approach used is universal and can be applied to other regions for looking at building vulnerability.
At the request of Canada Mortgage and Housing Corp., testing of traditional and rainscreen stucco systems was added to the research project. B.C. Wall & Ceiling Association acted as consultants, providing the typical detailing of current stucco practice to be tested. Both systems tested well.
The influence of stucco on overall structural performance was dramatic, says Taylor who was surprised by the results.
With some refinements to the stucco system, a two storey single family home would suffer minor cracks around...