Q.: For a school, I recently poured radius stairs with six risers and five treads with an arc length of about 25 feet at the bottom. Mostly due to an icing problem, the architect and the city condemned the stairs, claiming that there were unacceptable tread widths. The treads were specified at 12 inches and the final product came in at 3/8 inch. The city claims that the allowable variation was 3/8 inch from the widest to the narrowest and they quoted UBC section 1003.3.3.3. Are there other guidelines for concrete stairs, and should't I be given the opportunity to correct the deficiencies before they are allowed to condemn the stairs and refuse payment?
A.: It certainly seems that you should be allowed to make corrections, but that depends on your contract. As far as the tolerances on the steps, ACI 117, Tolerance (section 4.4.1), states that the cross-sectional dimension of any member that is specified at 12 inches or less is +3/8 inch and 1/4 inch from the specified dimension. ACI 117 (section 4.5.1) goes on to say that for stairs the maximum difference in height between adjacent risers is 1/8 inch and the maximum difference in width between adjacent treads is 1/4 inch.