Sandy, UT Earthquake Safety: Foundation Anchoring (2026)

Under the 2021 IRC Section R403.1.6 (as adopted by Utah and applied by the GSL MSD), wood foundation sill plates and bottom plates of braced wall panels must be anchored to concrete or masonry foundations with 1/2-inch diameter (or larger) anchor bolts embedded at least 7 inches into concrete or grouted masonry. Bolt spacing is a maximum of 6 feet on center (4 feet for one- and two-story buildings in Seismic Design Categories C, D0, D1, D2), with bolts located not more than 12 inches from each end of every plate section. In Salt Lake County's SDC D2, all anchor bolts in braced wall lines must include 3-inch by 3-inch by 1/4-inch steel plate washers between the sill plate and nut, or approved anchor straps (per IRC R602.11.1). Cripple walls (short stud walls between foundation and floor) must be sheathed with structural panels on the exterior and anchored top and bottom. The minimum frost depth for footings is 30 inches; standard allowable bearing pressure is 1,500 psf (per GSL MSD design criteria). Site-specific ground-motion parameters must be obtained using the ATC Hazard Tool because shaking intensity varies substantially across the Salt Lake Valley. Existing pre-1975 wood-frame homes are generally NOT subject to mandatory foundation-bolt retrofit; the Fix the Bricks program (administered by Salt Lake City Housing Stability) addresses URM houses with roof-to-wall straps and chimney bracing — not wood-frame sill-plate bolting. Voluntary retrofit using FEMA P-1100 or Utah Guide for Seismic Improvement of URM Dwellings is encouraged.