Developing earthquake standards for cities is hard enough, but writing rules to strengthen homes to withstand serious temblors—rules that apply to a large number of homes, including those built on hillsides, and are flexible enough to use a variety of materials and building techniques—is a challenge.
But that’s what the Berkeley City Council decided to do at its meeting last week, voting unanimously to approve a resolution authored by Councilmember Laurie Capitelli asking staff to review current standards and report back to council with suggested changes within one year.
At issue is the Disaster Commission’s goal of maximizing the number of Berkeley homes that will withstand a major earthquake.
Following the 1989 Loma Prieta earthquake, the city, in 1991, wrote new laws providing incentives to get people to retrofit their homes. The measure allowed homeowners, at the time a home is sold, to use one-third of their transfer tax burden —equal to 0.5 percent of the selling price—to pay for the costs of retrofitting their homes.
In 1991, there were no standards written for the retrofit. “It depended on the contractor,” said Jesse Townley, Disaster and Fire Safety Commission chair in a phone interview Friday.
When experts went under houses to check work that had been done under the 1991 law, they found some homes were insufficiently protected and others had work that was excessive, Townley said.
“Less than one-third of the retrofits were properly performed,” says a staff report, prepared for the May 8 City Council meeting.
This problem led to the adoption in February of retrofit standards, known as Plan Set A. But this standard has a limited value, applying only to homes constructed in simple box shapes, one or two stories high, located on relatively flat lots, which have a wood frame, are at least 1,200 square feet and have less than a 4-foot crawlspace under the house.
For homeowners who want to take advantage of the tax rebate, but whose houses do not fall into the Plan Set A category, they must get an engineer’s report before they can get the work done. This will often cost more than the rebate and may act as a disincentive to do the work, Townley said.
For those able to take advantage of Plan Set A, many find the standard too rigid, Townley said, specifying, for example, precise materials and techniques that must be used. Were Plan Set A more flexible, various types of bolts could be used—in some cases one might be able to use fewer bolts of greater strength, in the end, producing the same benefit, Townley said.
There are different equivalencies that should be written into the standards, Townley said. “It may be cheaper to do the same thing differently.”
Another problem raised is that Plan Set A identifies some materials by their product name. “We do not believe the city of Berkeley should be a sales outlet for a hardware manufacturer,” wrote Disaster Commissioner Kyle McCormick and former Commissioner Howard Cook in an undated letter addressed to Councilmember Kriss Worthington “et al.”
In addition to addressing the question of drawing up more flexible guidelines for Plan Set A, the council asked staff on May 8 to review new Los Angeles hillside building codes adopted in 2007, for possible implementation in the Berkeley hills. These guidelines were adopted in Los Angeles in response to the 1994 Northridge earthquake.