Floor Flatness (FF) 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.
How is FF FL calculated?
To calculate FL, add the absolute value of the z mean to three times the standard deviation, then invert the number. Flatness numbers are on a scale of 10 to 150, and most slabs fall in the range of 15 to 100. The minimum FL and FF values needed will depend on the building type.
What is the tolerance of a concrete slab?
Traditionally allowable tolerances of concrete floor slabs were determined by checking the slab surface with a 10 foot straightedge. Common tolerances were 1/8 inch or 1/4 inch in 10 feet.
What does a floor levelness of 20 mean?
moderately flat
FF/FL numbers have the following floor flatness classifications: FF 25/ FL 20 – moderately flat. FF 35/ FL 25 – flat. FF 45/ FL 35 – very flat.
How does FF FL work?
Floor Flatness (FF): The FF number essentially tells you how flat your concrete floor is. Floor Levelness (FL): The FL number indicates if you have any tilts or pitches in the slab. The more level your slab, the higher your number. These two numbers work together to control levelness and flatness.
What are FF FL numbers?
Ff, or “flatness F-Number,” defines the maximum floor curvature allowed over 24″ (600 mm) computed on the basis of successive 12″ (300 mm) elevation differentials. Fl, or “levelness F-Number,” defines the relative conformity of the floor surface to a horizontal plane as measured over a 10′ (3.03m) distance.
What is tolerance in concrete construction?
Tolerances are a means to establish permissible variation in dimension and location, giving both the designer and the contractor limits within which the work is to be performed.
Is code for tolerance in construction?
The tolerance shall be 2995 – 2985 9 10 mm. The basic dimensions with tolerances shall be expressed as 2990 f 5 mm.
What is FF level?
What is FF in construction?
Also referred to as FF is Finished Floor Elevation. The term FFE refers to the top of the structural slab and its elevation above sea level. FG. Finished grade. The term FG refers to the elevation above sea level for the finished grade or finished ground.
What is FF and FL testing?
Floor flatness (FF) and levelness (FL) numbers determine whether a floor is sufficiently smooth and level, respectively, as constructed. The test should be conducted within 72 hours of finishing the slab, as the curing process could cause the slab to curl and deviate from the flatness achieved by the finishers.
What is acceptable floor slope?
Floor slope is not uncommon, especially in homes more than 15 years old. According to the National Association of Home Builders (NAHB), floor slopes less than ½ inch (1.27 cm) over a distance of 20 feet (6.10 meters) are acceptable. Other experts say that anything under 1.5 inches (3.8 cm) is okay.
Do flfl tolerances apply to cambered or suspended floor slabs?
FL (levelness) tolerances do not apply to cambered or suspended floor slabs. Floor tolerances MUST be measured within 72 hours following construction if they are to be used for conformance purposes.
What is the reference table for specifying FF/fl tolerances?
CSA A23.1 includes reference tables for specifying FF/FL tolerances. ACI302 and ACI 117 discuss the recommended practices for floor construction and tolerance achievement. FF80 is twice as flat as FF40 and FF40 is twice as flat as FF20.
What is the tolerance of a jointed concrete floor?
Constructed floor tolerances generally decline as the concrete dries in jointed floors because of curling of slab edges caused by the normal drying shrinkage of the concrete. Tolerance losses of up to 50% may occur. Fmin tolerances do not apply to random traffic areas and FF/FL tolerances do not apply to defined traffic areas.
What does the faff L number tell you about the concrete?
F L 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.
