Warning about "1/8-inch-in-10-feet" Tolerances

Some designers and public agencies continue to specify the often used "1/8-inch-in-10-feet" tolerance for floors. It's a poor way to specify floors. The December 1983 issue of the American Concrete Institute's Concrete International, page 6, contains the following warning:

"In studies of finishing tolerances of in-place floor slabs conducted by ACI Committee 117, Tolerances, the indication is that the commonly specified floor finish tolerance of "1/8-inch-in-10-feet" is not being acheived except in special use floors employing highly specialized placement and finishing techniques.

Architects, engineers, and specifiers are cautioned against using this tolerance except where required for special use such as the drive aisles of high lift fork truck warehouses. Contractors are cautioned that the "1/8-inch-in-10-feet" tolerance requires highly specialized placement and finishing techniques.

Industry standard procedures involving high production placing and finishing techniques are producing serviceable floors which do not conform to the "1/8-inch-in-10-feet" finish tolerance. Indiscriminate use of this tolerance when not needed may raise the potential of unnecessary contractual and legal disputes.

ACI Committee 117 recommends the use of finish tolerances contained in "Standard Tolerances for Concrete Construction and Materials (ACI-117-81)," taking into consideration the intended use of the floor and construction materials used. Committee 117, working in conjunction with Committees 301, 302, and 318, hopes to provide a better defined finish tolerance and measuring techniques in the near future."