Finished Concrete Floor Flatness

Tom klemens the dipstick tool is the typical measurement taken for flatness the morning after concrete is placed.

Finished concrete floor flatness.

The ffnumber relates to the rate of change of the elevation of a concrete floor over a 12 interval. Specifically joints and cracks curl making the floor less flat with the passage of time. Aci staff 2008 concrete q a. Common tolerances were 1 8 inch or 1 4 inch in 10 feet.

American concrete institute aci 301 16 specifications for structural concrete. Concrete floor slab flatness and levelness traditionally allowable tolerances of concrete floor slabs were determined by checking the slab surface with a 10 foot straightedge. F numbers were developed in the 1980s to provide a systematic quantitative way to indicate the flatness and levelness of a concrete floor. Both numbers are dimensionless and the higher the number the more accurate the floor construction.

Aci 117 begins by defining what the tolerances mean in terms of such things as bowing deviation flatness and levelness and provides drawings to help explain these terms. Due to concrete shrinkage and slab curling ff fl numbers diminish with time. For the concrete contractor flatness is specified as an ff number and levelness as an fl number. This was measured by laying a 10 foot straightedge on the finished floor and measuring the greatest gap below the straightedge.

Floor flatness levelness one of the things that distinguishes a high tolerance floor is its f number requirement. The higher the f number the flatter or more level the floor. Concrete contractor pours the concrete and finishes it to the specified floor flatness requirement as stated in aci 117 specification for tolerances for concrete construction and materials the f. Rejecting floors based on one sample measurement line concrete international jul pp.

This method worked quite well for decades. Floor flatness f f controls the bumpiness of the floor surface and is primarily affected by the finishing operations after screeding including restraightening and power floating. Material tolerances are in section 2 including the location tolerance for reinforcing bars which varies depending on the thickness of the concrete member. Ff flatness is most affected by the finishing operation.

Fl levelness is most affected by forming and strike off. History of concrete floor flatness and floor levelness traditionally concrete floors were specified to have a deviation of less than 1 8 over 10 feet.