Unattached frame garages and sheds 600 square feet or less shall be built on a concrete slab no less than 4 inches thick and 4 inches wide for a 24-inch rat wall. Anchor bolts (minimum 1/2 inch diameter) shall be set 2 inches above and 7 inches below concrete, 6 feet on center and within 1 inch of corners with 2 anchors minimum (per wall section).
Masonry garages and masonry fronts on frame garages and all structures over 600 square feet must be built on a foundation or footing at least 12 inches wide that extends at least 42 inches below finished grade to undisturbed soil. On all construction attached to and made structurally a part of the residence, a 42-inch foundation or footing is required.
Concrete shall be designed to have a minimum compressive strength of 3,500 pounds per square inch (psi) at 28 days. If air-entrained concrete is used, the ultimate compressive strength may be reduced to 3,000 psi at 28 days.