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// CODE SNIPPET

722.2.2.1 Reinforced and Prestressed Floors and Roofs

2014 FBC - Building, 5th edition > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.2 Concrete Assemblies > 722.2.2 Concrete Floor and Roof Slabs > 722.2.2.1 Reinforced and Prestressed Floors and Roofs
JUMP TO FULL CODE CHAPTER

The minimum thicknesses of reinforced and prestressed concrete floor or roof slabs for fire-resistance ratings of 1 hour to 4 hours are shown in Table 722.2.2.1.

TABLE 722.2.2.1
MINIMUM SLAB THICKNESS (inches)

CONCRETE TYPEFIRE-RESISTANCE RATING (hours)
111/2234
Siliceous3.54.356.27
Carbonate3.244.65.76.6
Sand-lightweight2.73.33.84.65.4
Lightweight2.53.13.64.45.1
For SI: 1 inch = 25.4 mm.

722.2.2.1.1 Hollow-Core Prestressed Slabs

For hollow-core prestressed concrete slabs in which the cores are of constant cross section throughout the length, the equivalent thickness shall be permitted to be obtained by dividing the net cross-sectional area of the slab including grout in the joints, by its width.

722.2.2.1.2 Slabs With Sloping Soffits

The thickness of slabs with sloping soffits (see Figure 722.2.2.1.2) shall be determined at a distance 2t or 6 inches (152 mm), whichever is less, from the point of minimum thickness, where t is the minimum thickness.

For SI: 1 inch = 25.4 mm.

FIGURE 722.2.2.1.2
DETERMINATION OF SLAB THICKNESS
FOR SLOPING SOFFITS

722.2.2.1.3 Slabs With Ribbed Soffits

The thickness of slabs with ribbed or undulating soffits (see Figure 722.2.2.1.3) shall be determined by one of the following expressions, whichever is applicable:

For s > 4t, the thickness to be used shall be t
For s ≤ 2t, the thickness to be used shall be te
For 4t > s > 2t, the thickness to be used shall be
(Equation 7-5)
where:
s=Spacing of ribs or undulations.
t=Minimum thickness.
te=Equivalent thickness of the slab calculated as the net area of the slab divided by the width, in which the maximum thickness used in the calculation shall not exceed 2t.
For SI: 1 inch = 25.4 mm.

FIGURE 722.2.2.1.3
SLABS WITH RIBBED OR UNDULATING SOFFITS

Related Code Sections


722.2.2.1 Fire and Smoke Protection Features, Reinforced and Prestressed Floors and Roofs
The minimum thicknesses of reinforced and prestressed concrete floor or roof slabs for fire-resistance ratings of 1 hour to 4 hours are shown ...
2014 FBC - Building, 5th edition > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.2 Concrete Assemblies > 722.2.2 Concrete Floor and Roof Slabs > 722.2.2.1 Reinforced and Prestressed Floors and Roofs
722.2.2.1 Fire and Smoke Protection Features, Reinforced and Prestressed Floors and Roofs
The minimum thicknesses of reinforced and prestressed concrete floor or roof slabs for fire-resistance ratings of 1 hour to 4 hours are shown ...
2017 FBC - Building, 6th edition > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.2 Concrete Assemblies > 722.2.2 Concrete Floor and Roof Slabs > 722.2.2.1 Reinforced and Prestressed Floors and Roofs
722.2.2.1 Fire and Smoke Protection Features, Reinforced and Prestressed Floors and Roofs
The minimum thicknesses of reinforced and prestressed concrete floor or roof slabs for fire-resistance ratings of 1 hour to 4 hours are shown ...
2020 FBC - Building, 7th edition > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.2 Concrete Assemblies > 722.2.2 Concrete Floor and Roof Slabs > 722.2.2.1 Reinforced and Prestressed Floors and Roofs
722.2.2.1.2 Fire and Smoke Protection Features, Slabs With Sloping Soffits
The thickness of slabs with sloping soffits (see Figure 722.2.2.1.2) shall be determined at a distance 2 t or 6 inches (152 mm), whichever is less ...
2020 FBC - Building, 7th edition > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.2 Concrete Assemblies > 722.2.2 Concrete Floor and Roof Slabs > 722.2.2.1 Reinforced and Prestressed Floors and Roofs > 722.2.2.1.2 Slabs With Sloping Soffits
722.2.2.1.3 Fire and Smoke Protection Features, Slabs With Ribbed Soffits
The thickness of slabs with ribbed or undulating soffits (see Figure 722.2.2.1.3) shall be determined by one of the following expressions, whichever ...
2014 FBC - Building, 5th edition > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.2 Concrete Assemblies > 722.2.2 Concrete Floor and Roof Slabs > 722.2.2.1 Reinforced and Prestressed Floors and Roofs > 722.2.2.1.3 Slabs With Ribbed Soffits
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