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Stem-Wall House

Two types of houses built before 1979—"stem-wall” and “cripple-wall”—may benefit from retrofitting with foundation anchoring, which reduces the possibility of a house sliding off of its foundation in an earthquake.

“Stem-wall” houses have a wood-framed first floor resting directly on a raised concrete perimeter foundation. The stem-wall retrofit consists of bolting the house sill plate to the foundation using foundation plates.

“Cripple-wall” houses have a short perimeter wall between the foundation and the wood-framed first floor. A cripple-wall retrofit consists of anchor-bolting the base of the wood frame to the concrete foundation and bracing the cripple walls.

Foundation Anchors: Bolting Raised Concrete Perimeter Foundations

“Foundation anchorage” describes both foundation bolts and foundation plates, and either can be used to secure a house frame to its foundation. For detailed information about foundation anchors, including which method to use, visit Earthquake Brace + Bolt.

New foundation anchorage can be installed by a licensed contractor according to a standard plan set for seismic retrofits, if your community has adopted such a plan set and your foundation meets plan-set requirements. Typically, Plan Set A is used in Northern California, and Standard Plan Set 1 is used in Southern California.

If your house does not have a raised continuous concrete foundation, or if it is not a wood-framed house, you should hire a licensed structural or civil engineer to advise on your retrofit efforts.

Strengthen Your House

Earthquake Brace + Bolt (EBB) offers up to $3,000 toward a code-compliant seismic retrofit for houses that qualify. An EBB seismic retrofit will help prevent your house from sliding off its foundation and lessen the potential for damage during an earthquake.

See if your home qualifies for $3,000 toward a seismic retrofit

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