Floor flatness is a measurement taken that reflects the flatness of a concrete floor after it’s pour. The technical way of measuring floor flatness is as follows:
“Floor flatness (FF) controls the bumpiness of the floor surface and is primarily affected by the finishing operations after screeding, including restraightening and power floating. Essentially, FF numbers evaluate the elevation differences along a sample line at one-foot intervals. F numbers extend from zero to infinity so the higher the F number, the flatter the floor.”
Flatness should be measured as soon as possible, preferably within 24-hours after concrete placement but no later than 72 hours.