DipstickWhat are F-Numbers?

ACI 117 is the industry standard for specification and measurement of concrete floor flatness (FF) and floor levelness (FL) commonly referred to as F-numbers. The F-numbers identify and control floor characteristics which are critical to the floor’s usefulness. A higher F-number always denotes a better floor.


Floor Flatness (FF) refers to the bumpiness of the floor while Floor Levelness (FL) refers to the tile or pitch of the slab.

ACI 117 provides surface classification which provides consistency and industry standards. Levelness is important because it affects shelf placement design, drainage and heavy equipment specifications. Flatness is important because it affects flooring installation, ride quality, drainage and safety in floors.

As the need for superflat floors continues to rise, contractors can count on MAKO to deliver a cost-effective and accurate solution for every job. With MAKO Screed Support Systems, finishers can rest assured the established elevation of concrete has been maintained and higher FF/FL numbers can be achieved in a shorter amount of time providing a superior slab.