What are F-Numbers?
The F-Number System is the American Concrete Institute (ACI117) and Canadian Standard Association (CSA A23.1) standard for the specification and measurement of concrete floor flatness and levelness. F-Numbers replace the familiar "1/8 inch in ten feet" type specs that had proven unreliable, unmeasureable and unrealistic.
The new standards include two F-Numbers:
FF for flatness and FL for levelness
Flatness relates to the bumpiness of the floor, while levelness describes the local tilt or pitch of the slab. The higher the F-Number, the bettr the characteristic of the floor. F-Numbers are linear, so an FF 20 is twice as flat as an FF 10, but only as half as flat as an FF 40.
The ACI/CSA F-Numbers System applies to 99% of all floor slabs - all floors that support random traffic be it vehicular or pedestrian traffic.
What F-Numbers equals 1/8" in 10'?
There is no F-number equivalent to any straightedge spec. But, rough equivalents, in terms of horizontal envelopes, can be given.
An FF 25 is roughly equivalent to a single 1/4" defect in 10'
An FF 50 is roughly equivalent to a single 1/8' defect in 10'
An FF 100 is roughly equivalent to a single 1/16" defect in 10'
