Quick Answer: San Jose homes have three main foundation types depending on when they were built: (1) Raised foundation / crawl space (most common in homes built before 1960) — the home sits on a perimeter foundation wall with a crawl space underneath; this type is most susceptible to cripple-wall earthquake damage and wood rot from moisture in the crawl space; (2) Slab-on-grade (most common post-1960 tract homes and modern construction) — a concrete slab poured directly on the ground; very stable, no crawl space to maintain, but slab cracks can indicate settlement; (3) Basement foundation (rare in San Jose — more common in pre-1940 homes in older neighborhoods) — a full below-grade floor under the house. The easiest way to identify your foundation: look in your garage or access the crawl space — if you see a crawl space beneath the floor, it’s a raised foundation; if the floor is solid concrete with no access below, it’s slab-on-grade.
San Jose Foundation Types by Era
| Foundation Type | Common In | Identifies As | Key Issues to Watch |
|---|---|---|---|
| Raised / Perimeter + Crawl Space | Pre-1960 homes | Elevated floor, access hatch to crawl space under house | Cripple wall earthquake risk; wood rot; moisture |
| Slab-on-Grade | Post-1960 tract homes | Solid concrete garage floor, no crawl space | Cracks from settlement; plumbing access difficult |
| T-Foundation (raised with stem wall) | 1950s-1970s | Short perimeter wall above grade, crawl space inside | Needs anchor bolts and cripple wall bracing per current seismic code |
| Post-and-Pier | Older homes, hillside lots | Visible concrete piers or wood posts under house | Very susceptible to seismic damage; piers may not be anchored |
| Daylight Basement | Pre-1940 homes | Full lower level, partially below grade | Water intrusion if drainage inadequate; older concrete may spall |
Quartz Construction assesses foundation condition as part of any renovation that requires a structural evaluation — room additions, second story additions, and seismic retrofit projects. Learn about foundation services. CSLB #1003436 | Call (650) 749-7436.
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