Cripple wall foundations require seismic bracing
FEMA P-2325 §FEMA Mitigation Recommendations (Earthquake)Description
Houses with cripple walls (short wood-stud walls between the concrete foundation and first-floor framing) should be braced with plywood or oriented-strand-board sheathing on the interior face of the cripple wall in seismic-active areas. Unbraced cripple walls are a primary cause of older-home collapse in earthquakes.
Why this exists
Per FEMA P-2325: 'homes with cripple wall foundations (with wood foundation walls) are inherently weaker and can collapse in an earthquake unless they have been seismically retrofitted.' This is one of the most predictable failure modes for pre-1970s California wood-frame construction.
Categories
Source
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Continuous load path from roof to foundation · HUD RSDG §2.4
- Residential structural reliability targets 1-in-100 to 1-in-1000 annual probability of failure · HUD RSDG §2.5
- Residential floor live load: 40 psf minimum (30 psf sleeping rooms) · HUD RSDG §3.4
- Wind load design uses ASCE 7 basic wind speed for the locality · HUD RSDG §3.6
- Ground snow load for Virginia: 25 psf eastern, up to 40 psf western mountains · HUD RSDG §3.7
Last reviewed 2026-05-11.