ACI Floor Flatness & Levelness (FF/FL Numbers)

Question 1

What do FF and FL numbers measure in concrete slabs?

Accepted Answer

FF measures local surface waviness; FL measures overall slope relative to a horizontal datum

Answer

FF measures slab thickness; FL measures compressive strength

Answer

FF measures surface hardness; FL measures moisture content

Answer

FF measures joint spacing; FL measures crack width

Question 2

What does a higher FF or FL number indicate about a concrete floor?

Accepted Answer

A flatter and more level floor with smaller deviations

Answer

More surface defects and cracks

Answer

Greater slab thickness

Answer

Lower compressive strength

Question 3

Which ACI document includes F-number tolerances for floor flatness and levelness?

Accepted Answer

ACI 117

Answer

ACI 301

Answer

ACI 318

Answer

ACI 360R

Question 4

What instrument is most commonly used to measure floor flatness F-numbers per ASTM E1155?

Accepted Answer

Dipstick profiler

Answer

Steel straightedge

Answer

Laser level

Answer

Digital micrometer

Question 5

What minimum FF number is typically specified for superflat floors used in very narrow aisle (VNA) warehouses?

Accepted Answer

FF 100

Answer

FF 25

Answer

FF 50

Answer

FF 75

Question 6

The F-number system was developed primarily to replace which older floor flatness measurement method?

Accepted Answer

The 10-foot straightedge method

Answer

Profilograph readings

Answer

Carpet-bombing elevation surveys

Answer

Mercury level readings

Question 7

Who is credited with developing the F-number floor flatness and levelness system?

Accepted Answer

Allen Face

Answer

Joseph Phelan

Answer

Robert Ytterberg

Answer

James Warner