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