California’s older housing stock was largely built before modern seismic codes, and the most common weakness is simple: the house is not adequately connected to its foundation. In a quake the structure can slide off, and the cripple wall — the short framed wall in the crawl space — can collapse. A brace-and-bolt retrofit fixes both by anchoring the mudsill to the foundation with bolts and bracing the cripple wall with structural plywood.
It is one of the highest-return safety upgrades a homeowner can make. The work is well-defined, permitted as a standard structural job, and usually completed in a few days without anyone moving out. California’s Earthquake Brace + Bolt (EBB) program even grants up to $3,000 toward the cost for eligible pre-1980 homes in participating ZIP codes, and the California Earthquake Authority discounts premiums for a documented retrofit.
Not every home needs the same scope. Soft-story buildings — living space cantilevered over a garage or tuck-under parking — need engineered solutions beyond a basic brace-and-bolt. Homes on a slab rather than a raised foundation have a different risk profile entirely. Chimneys, water-heater strapping, and automatic gas shutoff valves are smaller items worth checking.
For a buyer: ask whether a retrofit has been done and get the permit record. An unretrofitted older home is not a dealbreaker — it is a budget line and a negotiating point. Knowing the foundation type and cripple-wall condition before the offer is exactly the kind of read the inspection should surface.