Bolt and Brace Seismic Retrofit to Help Prevent Earthquake Damage
CA Dept. of Insurance Commissioner Dave Jones: “The natural disasters of 2017 remind us of the need to be prepared for the major earthquakes that are inevitable in California… Californians can protect their families by strengthening older homes, which are particularly vulnerable to earthquake damage, and by making sure they have the financial strength to rebuild with earthquake insurance.”
Homes with qualifying retrofits are eligible for discounts of up to 20 percent on CEA earthquake insurance premiums.
Bolting the house to the foundation, bracing the area above the foundation, and bolting the main floor can reduce the risk of earthquake damage to your home.
Bolting to Prevent Seismic Damage
Bracing to Prevent Seismic Damage
More than 1.2 million houses in high-hazard areas of California are particularly vulnerable to earthquakes because of the type of construction, according to the CEA. These homes are typically built before 1979, have a wood frame on a raised foundation and have a cripple wall in the crawl space under the house.
Most houses need to be seismically retrofitted in three ways: 1. The cripple walls of the house need to be braced with plywood. 2. The house needs to be bolted to the foundation. 3. The floor of the house needs to be attached to the braced cripple walls with shear transfer ties. These three steps serve to seismic retrofit and bolt a house to the foundation by converting the cripple walls into shear walls.
If any one of these three areas is not made earthquake resistant with a seismic retrofit, your un-retrofitted house can slide off of its foundation.
Above the first floor, interior finishes on the walls and partitions such as plaster, though not designed to resist earthquakes, do in fact provide a lot of earthquake resistance. Therefore, this part of the house above the crawl space does not need further bolting. The failures always occur in the crawl space, which is where the house needs to be bolted to the foundation here as well as convert the cripple walls into shear walls.
We have experience in all aspects of the construction trade with over 20 years of building experience in the San Francisco Bay Area.
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