Unattached frame garages and sheds 600 square feet or less shall be built on a concrete slab not less than 4 inches thick with a 24-inch rat wall, 4 inches wide. Anchor bolts (minimum 1/2 inch diameter) shall be set 2 inches above and 7" below concrete, 6 feet on center and within 1’ 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.