Q: How careful do we have to be in making footings to the dimensions shown on the drawings?

A: Committee 347 of the American Concrete Institute has recommended the following tolerances for footings:

of concrete (not reinforcing bars or dowels)

Minus 1/2 inch or plus 2 inches

Misplacement or eccentricity of concrete (not reinforcing bars or dowels)

2 percent of the footing width in the direction of misplacement but not more than 2 inches

Reduction in thickness

Minus 5 percent of specified thickness