Dimensional Tolerances in Construction and for Surface Accessibility

1.1.8 Alternate measurement tools. Walks may be measured with instruments other than a digital inclinometer if they provide the data required for evaluation of tolerances as given in Sections 1.2.1, 1.2.2, and 1.2.3. If the F - number system is used pedestrian paths should have a minimum FF of 25. Running slope should be measured along the same lines of measurements as given in Section 1.1.3.

Although the F - number system can be used to measure surface flatness for smooth surfaces it requires expensive equipment and workers trained to do the measurement.

An FF of 25 provides for a flatness of approximately ¼ in. in 10 feet (6 mm in 3050 mm). Waviness index may be a more appropriate measure to include if floor profilers are used.