Question: We are building a shopping mall and we would like to know what the tolerances are on stairs. Who enforces these tolerances?

Answer: An extensive set of tolerances has recently been adopted by the American Concrete Institute. A summary of those pertaining to cast-in-place concrete was published in the October 1980 issue of Concrete Construction, which shows (page 747) the proposed tolerances to be:

These tolerances are given in ACI 117-81, "Tolerances for Concrete Construction and Materials." If this standard were referenced in the contract documents, its provisions would be enforceable. Its provisions might be assumed to be in effect even if not referenced in the contract documents.Your local building code may have a different set of provisions. For example, the BOCA Basic Building Code/1981 provides that the minimum for risers be 4 inches and the maximum 7 inches, while the minimum for treads be 11 inches and the maximum 14 inches. It also provides "There shall be no variation exceeding 3/16 inch in the depth of adjacent treads or in the height of adjacent risers, and the tolerance between the largest and smallest riser shall not exceed 3/8 inch in any flight."