Section 1907 Minimum Slab Provisions
The thickness of concrete floor slabs supported directly on the ground shall not be less than 31/2 inches (89 mm). A 6-mil (0.006 inch; 0.15 mm) polyethylene vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the base course or subgrade and the concrete floor slab, or other approved equivalent methods or materials shall be used to retard vapor transmission through the floor slab.
Exception: A vapor retarder is not required:
- For detached structures accessory to occupancies in Group R-3, such as garages, utility buildings or other unheated facilities.
- For unheated storage rooms having an area of less than 70 square feet (6.5 m2) and carports attached to occupancies in Group R-3.
- For buildings of other occupancies where migration of moisture through the slab from below will not be detrimental to the intended occupancy of the building.
- For driveways, walks, patios and other flatwork that will not be enclosed at a later date.
- Where approved based on local site conditions.
Concrete slabs-onground shall be provided with control and contraction joints in accordance with ACI 360 or other approved industry standards. Control and contraction joints shall be designed by an architect or engineer.
- Concrete slabs-on-ground shall contain micro- or macro-synthetic fiber reinforcement. Fiber length shall be 1/2 inch to 2.25 inches (13 to 56 mm) in length. Dosage amounts shall be from 0.75 to 3.0 pounds per cubic yard (0.45 to 1.78 kg/m3) in accordance with the manufacturer's recommendations. Synthetic fibers shall comply with ASTM C1116. The manufacturer or supplier shall provide certification of compliance with ASTM C1116 when requested by the building official; or,