Footings, foundation walls, and sill anchorage

Minimum footing sizeR403.1, Table R403.1(1)#

Footings for light-frame construction bear on undisturbed soil. Width and thickness depend on the number of stories and the load-bearing value of the soil. A minimum footing thickness of 6 inches is typical for concrete footings supporting one- and two-story dwellings. Check the adopted footing table for the width required at your soil class before pouring.

Footing projectionR403.1.1#

The footing must project beyond the face of the foundation wall on each side. The projection is limited so that unreinforced concrete footings do not fail in flexure. In general, the projection beyond the wall must not exceed the footing thickness for plain concrete.

Frost depthR403.1.4#

The bottom of exterior footings must be placed below the frost line of the locality. North Carolina jurisdictions typically adopt a 12 to 15 inch minimum frost depth, but the adopted local value governs. Interior footings in heated buildings may bear at a shallower depth when protected from frost.

Anchor bolts for sill platesR403.1.6#

Wood sill plates on concrete or masonry foundations must be anchored with 1/2 inch diameter anchor bolts spaced not more than 6 feet on center. A minimum of two bolts per plate section is required, with one bolt located not more than 12 inches and not less than 7 bolt diameters (3.5 inches) from each end of the plate section. Bolts must be embedded at least 7 inches into the concrete or grouted masonry. A nut and washer are required at each bolt.

Common inspection flags#

Typical footing and anchorage failures caught at footing and framing inspection:

• Footings poured on loose fill or organic topsoil instead of undisturbed soil
• Anchor bolts spaced wider than 6 feet or missing within 12 inches of a plate splice
• Anchor bolts installed without washers under the nut
• Footing width narrower than required for the soil class on the adopted table
• Brick ledge formed without the foundation wall centered on the footing