Determining FF (Floor Flatness) and FL (Floor Levelness) Numbers

Let us understand, how traditional floor installer and engineers followed the "Straight edge specification" for inspection of floor level and flatness:

In 1979, Allen Face developed the F-number system, officially called the Face Floor Profile Numbering System, which was later formalized into the ASTM E1155 and the ACI national standards. He later developed the Dipstick® Floor Profiler and the F-Meter®, the tools needed to take more accurate measurements than the straightedge method.

As per ASTM E 1155 – 96 and ACI 302.1, determination of FF (Floor Flatness) and FL (Floor Levelness) numbers can be tested at site level.

Floor Levelness (FL)
FL numbers provide information about the concrete floor's levelness. Levelness depicts how closely the finished floor matches the intended slope indicated in the design documents. Elevation differences are measured every 10-feet within 72 hours after the concrete is placed and those measurements are entered into a calculation to determine floor levelness (FL). Higher FL numbers indicate a more level floor and the numbers are linear so a FL of 50 is twice as level as an FL of 25.


Floor Flatness (FF)
FF numbers depict the Floor Flatness, or how close to planar the floor is. In other words, Floor Flatness is a statistical measurement of how wavy or bumpy a concrete floor is and takes into account the amplitude (height if the waves) and the wavelength (horizontal distance between waves). Elevation differences are taken every foot within 72 hours after the concrete is placed and a formula determines the FF measurement. As with FL, the measurements are linear and higher numbers represent a flatter floor. For example, a floor with an FF measurement of 60 is twice as flat as a floor with an FF of 30.

This test method provides

1. Statistical (and graphical) information concerning floor surface profiles.

2. Primarily we can establish compliance of randomly trafficked floor surfaces with specified FF Flatness and FL Levelness tolerances.

3. Evaluate the effect of different construction methods on resulting floor surface flatness and levelness.

4. Investigate the curling and deflection of floor surfaces.

5. Results of this test method shall not be used to enforce contract flatness and levelness tolerances on those floor installations primarily intended to support the operation of fixed path vehicle systems (for example, narrow aisle warehouse floors).

Location of Sample Measurement Lines on Test Section: 

Floors classification based on Flatness and Levelness according to ACI 117:

CLASSIFICATION	SPECIFIED OVERALL FLATNESS (SOFF)	SPECIFIED OVERALL LEVELNESS (SOFL)
Conventional	20	15
Moderately Flat	25	20
Flat	35	25
Very Flat	45	35
Super Flat	60	40

Super flat floors require special skill and equipment to achieve and should only be used for the most critical of concrete floors in specialized programs like television studios. Super flat floors may also be specified to have FF 100 and FL 50, but these are for defined-traffic (single direction of travel) installations such as narrow-aisle warehouses as opposed to a random-traffic floors that the ACI 117 standard covers.

American Concrete Institute publication ACI-302.1, the following FF and FL values are acceptable based on the uses:

USAGE	FLOOR FLATNESS (FF)	FLOOR LEVELNESS (FL)
Noncritical spaces, mechanical rooms, back-of-house, parking, areas to receive thick-set tile	FF 20	FL 15
General office, light industrial, carpeted spaces	FF 25	FL 20
General warehouse floors, areas to received thin-set tile, laboratories	FF 30-35	FL 20-25
Warehouses with air-pallet use, ice rinks	FF 45	FL 35
Movie and television studios	FF >50	FL >50

Let see the on-site testing video for testing the F Number of floor using Dipstick:

Where still accurate flatness is required, Floor profiler is used. Let see the on-site testing video for testing the F Number of floor using Floor Profiler:

From Concrete Society Technical Report 34 (TR 34):

For on site testing: CONCRETE PLANNER, 524, Udyog Vihar, Phase-5, Gurugram, Haryana, India. Pin: 122016, Email- Info@concreteplanners.com, Phone: +91-8505866600 

Many thanks for google.com, http://www.iceline.com, Dipstick Profiler, https://concretesociety.co.za, Parmeet Bhalla BGSB, CONCRETE PLANNER, from where the details are collected.