“Floors have historically been measured for flatness and levelness with the “straightedge” method. However, this method is inherently flawed due to the subjective nature of the test. In the 1970’s, Allen Face created the FL and FF systems to statistically measure these 2 key components of the floor. Levelness (FL) is defined as the variation in elevation between two points 10’ apart. Flatness (FF) is defined as the variation in elevation between two points 12″ apart. In Canada , typical specification for cast in place slabs are “FF25 and FL 15”. While there is no direct formulation to equate straight edge measurements to the the FF/FL system, a FF25/ FL 15 correlates closely to a “1/4 allowed gap under a 10’ straightedge”.
In the 1970’s Allen Face saw the need for a measurement system for “defined traffic” floors, where forklifts are typically guided by wires down the aisle ways. Guided wire lifts have become popular in “Very Narrow Aisle” warehousing of VNA for short, where racking typically can be 47’ tall with sometimes just an inch or two of clearance on each side. This requirement required a flooring specification that considered the wheel tracks of the lift, the desired speed and lifting height of the lifts as well. This requirement created the system of floor measurement called “F-Min”. Again, while there is no direct formula to equate F-min to FF/Fl values the following is a close approximation:
- F-Min 80= FF113/Fl 80 (minimum). This equals a maximum rate of change in 12” of .05”.
TC Floors West used many techniques and equipment to build such a VNA warehouse with an F-Min 80 warehouse, such as:
- floor scarifiers
- floor planers
- floor grinders
- shot blasters
- self levelling material pumps
The aisles were prepped then had a topping poured of Ardex SDT. After 24 hours, the process of specific grinding techniques would begin to further refine the aisle and chief the flatness required. At the end of each completion of an aisle, we used a “d-meter” that measures the floor every 12”, to verify that the specification has been attained.
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