Does Retrofit Really Work?
This fascinating true story was given to us courtesty of the American Plywood Association.
 Does retrofit really work? Read on.
In 1989, at the corner of Center and Elm streets in downtown Santa Cruz,
architect Michael O'Hearn unwittingly created a laboratory for the study of seismic retrofit design. His true story follows:
On that corner, at 214 and 210 Elm Street, were two identical Victorian style homes.
According to O'Hearn, the twins were built 95-100 years ago, by the same builder, with identical materials and using the same construction techniques.
When O'Hearn bought them in 1984, both houses had been through multiple remodels and O'Hearn remodeled the pair yet again.
He started by retrofitting #210, installing plywood shear panels on the cripple walls and bolting the mudsill to the foundation. Unfortunately, there was no time to retrofit #214 before the 7.1 Loma Prieta earthquake hit on Oct. 17, 1989.
In a sense, 214 Elm Street was the "control element" in this amazing experiment. "The building came apart in four sections," O'Hearn said.
However, 210 Elm Street, with its plywood shear panels and bolted foundation, suffered only minor damage. "The one we had retrofitted (210 Elm St.) cost us $5,000 to repair.
The other one (214 Elm St.) cost us $260,000 to repair. The whole building had to be jacked up, repaired, and slid back on a new foundation."
O´Hearn offers this advice, "For homes more than 20 years old located in areas of seismic activity, I strongly urge owners to consider seismic retrofit. It's alot cheaper to retrofit a house
now than to repair it after an earthquake."
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