WHAT ARE "F" NUMBERS?
THE "F" NUMBER IS A NEW AMERICAN CONCETE INSTITUTE (#117) AND CANADIAN STANDARDS ASSOCIATION (#A23.1)
STANDARD SPECIFICATIONS AND MEASUREMENT OF CONCRETE FLOOR FLATNESS AND LEVELNESS. F-NUMBERS
REPLACE THE FAMILIAR "1/8TH INCH IN TEN FEET" TYPE SPECS THAT HAD PROVEN UNRELIABLE, UNMEASUREABLE
AND UNREALISTIC.
THE NEW STANDARDS INCLUDE TWO "F"-NUMBERS:
FF = FOR FLATNESS (BUMPINESS OF THE FLOOR) FF25/FL20 EXAMPLE
FL= FOR LEVELNESS (TILT OR PITCH OF THE SLAB)
NOTE: THE HIGHER THE "F" NUMBER THE BETTER THAT CHARACSTERISTIC OF THE FLOOR
HOW ARE "F"-NUMBERS MEASURED?
"F"-NUMBERS ARE DERIVED FROM STATISTICAL ANALYSIS OF THE FLOOR'S ELEVATION MEASURED AT ONE-FOOT
INTERVALS. THE ELEVATION DIFFERENCES OVER TWO FEET TO DETERMINE FF WHILE THE DIFFERENCES
OVER TEN FEET ARE USED TO DETERMINE FL.
BASICALLY MEASUREMENT LINES ARE LAID OUT ON THE FLOOR AND ELEVATION MEASUREMENTS ARE TAKEN EVERY ONE
FOOT DOWN THE LINE. MEASUREMENTS LINES MUST BE AT LEAST 11 FEET LONG.
SINCE FF MEASUREMENTS REQUIRE TWO FOOT POINT SEPARATIO, THE FIRST FF MEASUREMENT CAN BE MADE
STARTING WITH THE SECOND FOOT OF EACH MEASUREMENT LINE. THE TWO-FOOT MEASUREMENT ARE CALLED "q"
VALUES
BECAUSE FL MEASUREMENTSREQUIRE A TEN-FOOT POINT SEPARATION, THE FIRST FL MEASUREMENT IS MADE
STARTING WITH THE TEN FOOT OF EACH MEASUREMENT LINE. THE TEN-FOOT MEASUREMNTS ARE CALLED "z"
VALUES
ENOUGH ELEVATION MEASUREMENTS SHOULD BE TAKEN SO THAT FOR EACH 1,000 SQUARE FEET OF FLOOR AREA, YOU TAKE AT LEAST
34 "z" VALUES.
DEPENDING ON THE FINISH TECHNIQUES, FLOOR FLATNESS/LEVELNESS CAN BE CONSIDERABLY DIFFERENT WHEN MEASURED "NORTH-SOUTH"
VS. "EAST-WEST" MEASUREMENT LINE. THEREFORE MEASUREMENT LINES MUST BE SELECTED TO BALANCE THESE POSSIBLE DIFFEENCES AND
ELIMINATE ANY DIRECTIONAL BIAS.
AFTER A COLLECTION, MEASUREMENTS ARE PUT INTO STANDARD MATHEMATICAL FORMULAE TO CALCULATE THE FLOOR'S "F"-NUMBERS.
SEVERAL DEVICES ARE APPROVED BY "ASTM" FOR "F"-NUMBER MEASUREMENT, INCLUDING THE DIPSTICK FLOOR PROFILER.
DETAIL RULES FOR PERFORMING "F-" NUMBER TESTS ARE SET FORTH IN "ASTM E-1155"
E1155 LOCATION OF SAMPLE MEASUREMENT LINES ON TEST SURFACES
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