Service

Seismic
Retrofit

Most Bay Area homes built before 1980 were not designed to current seismic standards. A properly engineered retrofit strengthens the connection between your home and its foundation so it can better resist earthquake forces.

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Why it matters

How earthquakes damage unretrofitted homes.

During an earthquake, the ground moves side to side while your home’s weight resists that motion. If the framing is not properly braced and anchored, the structure can rack, slide, or collapse. Homes with raised foundations and cripple walls are especially vulnerable. This is a common condition throughout Oakland and Berkeley.

A seismic retrofit targets the weakest points in this system: the connection between the wood framing and the concrete foundation, and the stability of the short cripple wall that sits between them. When both are properly addressed, the house behaves as a unified structure that stays attached to its foundation through strong shaking.

Common damage patterns

What happens without a retrofit.

Homes without proper anchorage and bracing fail in predictable ways. These are the most common ones a retrofit is designed to prevent.

Cripple wall racking under lateral load — Cripple walls without plywood bracing rack sideways under lateral forces.

Home sliding off cripple wall — Without proper fasteners and bracing, the home can shift off the cripple wall.

Home sliding off foundation — Homes without adequate anchor bolts can slide off the foundation during strong shaking.

Home overturning — Unbraced walls can allow the structure to overturn under severe lateral forces.

Properly retrofitted home remains attached — ✓ A properly retrofitted home remains securely attached to its foundation.

What we design

Key components of a seismic retrofit.

A retrofit addresses three interconnected systems. Each one must be properly designed and detailed for the overall system to perform.

Foundation Anchorage

Anchor bolts connect the wood sill plate to the concrete foundation. Many older homes either have no anchor bolts or have bolts spaced too far apart to meet current code. We specify bolt size, spacing, edge distances, and plate washers so the framing stays firmly attached to the concrete during strong shaking.

Plywood Shear Walls

Structural plywood panels are installed on the interior faces of the cripple walls to resist side-to-side movement. The nailing pattern, panel layout, blocking, and edge fastening are all critical to the wall’s performance. We size and detail each panel based on the actual forces acting on your home.

Hardware & Continuous Load Path

Metal connectors, holdown devices, and framing hardware tie the system together. These components ensure that seismic forces transfer from the floor framing into the shear walls and down into the foundation. A retrofit only works when the entire load path is continuous. We design the system as a whole, not as isolated pieces.

Foundation anchorage detail showing anchor bolts and plate washers — Foundation anchorage: anchor bolts and plate washers securing the sill plate to concrete.

Plywood shear wall panels installed on cripple wall framing — Plywood shear wall panels nailed to cripple wall framing.

Plywood shear wall panels installed in a crawl space during a seismic retrofit — Plywood shear wall panels installed in a crawl space during a retrofit.

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SeismicRetrofit