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Floor Finishing Specifications

ASCC Position Statement #25

Floor finish requirements are often included in the project specifications. This position statement presents issues for specifiers to consider before such issues cause a conflict on the job site. Addressing these issues in the specifications, or at the preconstruction meeting, will help the design professional and concrete contractor to satisfy the owner’s expectations. 

Specifiers often reference ACI 301-99, “Specifications for Structural Concrete,” which contains default flatness specifications. Unless otherwise specified, flatness and levelness F-numbers for floor installations exceeding 10,000 ft2 (1000 m2) in total project area are to be measured in accordance with ASTM E 1155 and must meet the F-number tolerances in ACI 117. ASCC concrete contractors concur with this requirement, and believe it to be superior to requirements using the gap under a 10 ft (3 m) straightedge method.

ACI 301 also has a default floor-finish tolerance requirement for a troweled and floated finish. The default is a finish that meets conventional straightedge tolerances specified in ACI 117. 

Unless the specifier states a floor finish tolerance, ACI 301 defaults to an overall 20/15 and a local 15/10 for flatness and levelness numbers, respectively. These tolerances may be too low to provide the needed flatness and levelness, and the specifier should consider specifying F-numbers that are more appropriate for the floor’s use.

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