Field Testing: 
Floor Slab F-Number Determinations performed using a FACE CO 2272 Digital Floor Profiler.
By Far The Best Accuracy
Testing labs, building owners, developers, contractors, universities, research institutions, and government agencies on six continents choose the Dipstick because it produces the most accurate and repeatable floor flatness and levelness data available in the industry. Contact us today to learn more.
Questions About F-Numbers
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. The F-Number system replaces the older “1/8 inch in ten feet” type specs that had proven unreliable, unmeasurable, and unrealistic.
The new standards include two F-Numbers: FF for floor flatness and FL for levelness.
Floor 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 better 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-Number System applies to 99% of all floor slabs – all floors that support random traffic, whether vehicular or pedestrian.
What F-Numbers Equal 1/8″ in 10′?
There is no direct F-number equivalent to any straightedge spec. However, rough equivalents, in terms of horizontal envelopes, can be provided.
- 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′.
