Footings must bear below the local frost depth: 30″ minimum at the SLC valley floor; 36″ in foothill communities (Draper, Sandy, Cottonwood Heights); 36–42″ in Wasatch Back communities (Park City, Heber City, Midway); and 42–48″ or more in mountain communities above 6,000 feet. These are minimums to the bottom of the footing — if poor soil bearing capacity requires going deeper to competent bearing strata, or if basement depth exceeds frost depth, the structure drives the excavation. On slab-on-grade applications, the perimeter footing must still reach frost depth even though the interior slab is near grade — a detail consistently missed by contractors unfamiliar with Utah frost requirements, producing heave damage that distorts door openings and cracks slabs within the first few winters.