In slab quality control, what do FF and FL denote in F-number ratings?

• A. Finish and Level
• B. Flatness and Levelness
• C. Frame and Length
• D. Fatigue and Longevity

Answer: (B)

FF and FL describe the surface geometry of a concrete slab. FF stands for flatness, which measures how evenly the surface runs across short spans. FL stands for levelness, which gauges how close the surface is to a true horizontal plane over the slab. Higher FF and FL values mean the surface more closely matches the intended flat and level condition, within the project’s tolerances. These ratings guide finishing, tolerances, and equipment placement to ensure the floor meets specifications. Other terms like finish and level or unrelated concepts aren’t part of the standard F-number terminology used here.