Seismic Retrofit Engineering

Protect Your Home
Before the Next Quake

Many Bay Area homes were built before modern seismic standards. A properly designed retrofit strengthens the connection between your house and its foundation so it can better resist earthquake forces. Permit-ready plans simplify approval and ensure a safe retrofit.

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Plywood shear wall installed in crawl space
Why it matters

Why Seismic Retrofitting Matters

During an earthquake, a house is pushed side to side by ground movement. If the framing is not properly braced and anchored to the foundation, the structure can rack, slide, or even collapse. Many homes with raised foundations and cripple walls are especially vulnerable.

A seismic retrofit focuses on strengthening the parts of the home that transfer these forces to the ground. When designed correctly, the system works together to keep the house securely attached to its foundation and reduce the risk of major structural damage.

Common damage patterns

How Earthquakes Damage Unretrofitted Homes

Homes that lack proper anchorage and bracing often fail in predictable ways. Below are common damage patterns seen in older houses that have not been retrofitted.

House cripple wall racking
Weak cripple walls without plywood bracing can rack sideways under lateral forces.
House sliding off cripple wall
Without proper fasteners and bracing, the home can shift off the short wall between the foundation and main floor.
House sliding off foundation
Homes without adequate anchor bolts can slide off the foundation during strong shaking.
House overturning
Severe shaking can cause overturning when walls are not properly braced and anchored.
House remaining attached to foundation
✓ A properly retrofitted home remains securely attached to its foundation.
What we design

Key Components of a Seismic Retrofit

Foundation Anchorage

Anchor bolts connect the wood framing of the house to the concrete foundation. Many older homes either have no anchor bolts or have bolts spaced too far apart to meet current standards.

During strong shaking, a house without proper anchorage can slide several inches off its foundation. We specify bolt spacing, edge distances, and plate washers in accordance with current code so the framing remains firmly attached to the concrete.

Plywood Shear Walls

In homes with raised foundations, short cripple walls between the foundation and the first floor are especially vulnerable. Without reinforcement, these walls can rack or collapse under lateral forces.

Structural plywood panels are installed to stiffen these walls and resist side-to-side movement. Proper nailing patterns, panel layout, blocking, and edge fastening are essential for the wall to perform as designed.

Hardware & Continuous Load Path

Metal connectors, holdown devices, and framing attachments tie the structure together. These components ensure that forces are transferred from the floor framing into the shear walls and down into the foundation.

A retrofit works best when the entire system is considered. When each connection is properly detailed, the house behaves as a single structural unit rather than a collection of separate pieces.

We prepare retrofit plans in accordance with the California Building Code and applicable local amendments. Our drawings are clear and organized, which helps minimize plan check comments and avoid unnecessary delays in permitting.
Retrofit detail connecting cripple stud to wood floor framing
Connection of cripple stud to wood floor framing.
Retrofit detail connecting sill plate to foundation
Connection of sill plate to foundation.

Ready to Strengthen Your Home?

If you are considering a seismic retrofit, we can evaluate your home and provide clear structural guidance on the next steps.

Schedule a Consultation