F303 Floor Slab-On-Grade Buildings
Slabs and foundations shall be constructed using a slab edge detail that eliminates cracks that could connect the house interior to subslab soil and is consistent with other construction constraints such as terrain. Monolithic slab construction should be used where possible. Only the following slab edge detail options may be used:
- Thickened edge monolithic — the subslab membrane shall extend beyond the outside face of the slab edge.
- Slab poured into stem wall — where concrete blocks are used as slab forms, the subslab membrane shall extend horizontally at least 1 inch (25.4 mm) into the stem wall, but shall not extend upward along any vertical faces of the stem wall. The concrete slab shall be poured into the stem wall to completely fill its open volume to form a continuous and solid stem wall cap of minimum 8 inch (203 mm) thickness. Framed exterior walls shall be sealed or gasketed to the slab.
- Slab capping stem wall — where the floor slab is formed and placed to completely cover the stem wall, the subslab membrane shall extend horizontally beneath the slab to its outer edge. The supporting stem wall shall be capped with a solid masonry unit of at least 4 inch (102 mm) thickness beneath the membrane and the slab.
Vertical joints through slabs shall be formed with a recess of not less than 1/4 inch by 1/4 inch (6.4 by 6.4 mm) and sealed with an approved sealant.
Plastic pipes shall be in contact with the slab along the slab's depth by casting the concrete tightly against the pipe. Where pipes are jacketed by sleeves, they shall be sealed by one of the following methods:
- Formation of a slot in the slab around the pipe and casting with asphalt or an approved sealant from the slab to a point above the sleeve, or
- Seal the space between the sleeve and the pipe with an appropriate joint sealant (see Section F303.6).
- Pipes and wiring penetrating the slab through chases or conduit shall be sealed by placing an approved sealant between the pipe or wiring and chase or conduit. Plastic sheath, foam or insulation material shall not be used alone around pipes or conduit for sealing purposes.
- Where multiple pipes are ganged, block out a work space around the multiple pipes and seal as in Section F303.3.4.2.
Mix designs for all concrete used in the construction of slab-on-grade floors shall specify a minimum design strength of 3,000 psi (20.7 MPa) at 28 days and a design slump not to exceed 4 inches (102 mm). On-site slumps shall not exceed 5 inches (127 mm), provided total water added to the mix including plant, transit and site added water does not exceed the following parameters:
- Slumps in excess of 5 inches (127 mm) shall be achieved through the use of mid-range or high-range water reducing admixtures. Water shall not be used in excess of the limitations.
- Slumps of concrete containing mid-range or high-range water reducing admixtures shall not exceed 8 inches (203 mm).
Concrete slabs shall be cured continuously after pouring according to one of the following procedures:
- Moist curing by means of ponding, fog spray or wet burlap for at least 7 days.
- Moist curing using impermeable cover sheet materials conforming with ASTM Cl71 for at least 7 days.
- Curing with liquid membrane forming compound according to manufacturer's specifications and conforming with ASTM C309.
Curing compounds shall be compatible with materials specified in Section F303.6.