Tempo:
SLABS Concrete slabs are used for basement floors and for houses or portions of houses constructed at grade. In small buildings, they are generally supported by the ground below and not by perimeter foundations.
Basement Floor Slabs Basement floor slabs are usually installed after a building has been closed-in, sewer and water lines installed and the basement floor drain put in place. These slabs should be at least 75 mm (3 in.) thick and slope toward the floor drain or sump pit. There should be at least one drain (or sump pit) located near the laundry area, if one is provided in the basement. Curing concrete gives off moisture that can seriously affect finish flooring, drywall or millwork. Therefore, the basement should be ventilated to allow moisture to escape before finish flooring or millwork is installed. Floor slabs separating conditioned space from the ground must be constructed with an air barrier system to prevent radon or other soil gases from entering. An effective air barrier system for floors-on-ground is provided by:
minimizing concrete cracks; providing a barrier material under the floor. In most cases, this will be accomplished by placing 0.15 mm (6 mil) polyethylene under the floor; and, sealing voids, joints and penetrations.
The usual construction sequence for a concrete floor slab is as follows: 1. Complete the installation of sewer lines and other subsurface work before the slab is placed. Compact backfill in trenches.
2. Place at least 100 mm (4 in.) of crushed rock or coarse gravel under the floor slab to restrict the passage of moisture by capillary action from the ground to the slab and to facilitate soil gas remediation if necessary. 3. Consider installing rigid polystyrene insulation over the gravel base in cold climates, when the basement may contain habitable space, or when the basement floor slab will be heated. 4. Apply the layer of 0.15 mm (6 mil) polyethylene sheet below the slab to dampproof the floor and provide a barrier to soil gas, including radon, and seal it to the foundation wall at the perimeter. Where the water table is high, waterproofing the slab will be necessary. 5. To allow for slight movement due to shrinkage of the slab during drying and settling of the sub-base, provide a pre-moulded joint filler or double layer of sheathing paper, or extend the under-slab polyethylene (Figure 41 on p. 74) between the floor slab and wall or column. Seal the joint filler, sheathing paper or polyethylene to the polyethylene air barrier/ dampproofing membrane on the wall to keep radon from entering the living space. 6. Place and consolidate the concrete, then strike it off with a straightedge to the proper elevation. This can be determined by measuring down from the bottom of properly levelled floor joists. In order to eliminate local high or low areas and to embed large aggregate particles, the surface is then immediately smoothed using a large darby or bull-type float or by other appropriate means. Tools used for air-entrained concrete should have a magnesium surface. Take care not to overwork the concrete, because this will result in a less durable surface.
Basement Floor Slabs Basement floor slabs are usually installed after a building has been closed-in, sewer and water lines installed and the basement floor drain put in place. These slabs should be at least 75 mm (3 in.) thick and slope toward the floor drain or sump pit. There should be at least one drain (or sump pit) located near the laundry area, if one is provided in the basement. Curing concrete gives off moisture that can seriously affect finish flooring, drywall or millwork. Therefore, the basement should be ventilated to allow moisture to escape before finish flooring or millwork is installed. Floor slabs separating conditioned space from the ground must be constructed with an air barrier system to prevent radon or other soil gases from entering. An effective air barrier system for floors-on-ground is provided by:
minimizing concrete cracks; providing a barrier material under the floor. In most cases, this will be accomplished by placing 0.15 mm (6 mil) polyethylene under the floor; and, sealing voids, joints and penetrations.
The usual construction sequence for a concrete floor slab is as follows: 1. Complete the installation of sewer lines and other subsurface work before the slab is placed. Compact backfill in trenches.
2. Place at least 100 mm (4 in.) of crushed rock or coarse gravel under the floor slab to restrict the passage of moisture by capillary action from the ground to the slab and to facilitate soil gas remediation if necessary. 3. Consider installing rigid polystyrene insulation over the gravel base in cold climates, when the basement may contain habitable space, or when the basement floor slab will be heated. 4. Apply the layer of 0.15 mm (6 mil) polyethylene sheet below the slab to dampproof the floor and provide a barrier to soil gas, including radon, and seal it to the foundation wall at the perimeter. Where the water table is high, waterproofing the slab will be necessary. 5. To allow for slight movement due to shrinkage of the slab during drying and settling of the sub-base, provide a pre-moulded joint filler or double layer of sheathing paper, or extend the under-slab polyethylene (Figure 41 on p. 74) between the floor slab and wall or column. Seal the joint filler, sheathing paper or polyethylene to the polyethylene air barrier/ dampproofing membrane on the wall to keep radon from entering the living space. 6. Place and consolidate the concrete, then strike it off with a straightedge to the proper elevation. This can be determined by measuring down from the bottom of properly levelled floor joists. In order to eliminate local high or low areas and to embed large aggregate particles, the surface is then immediately smoothed using a large darby or bull-type float or by other appropriate means. Tools used for air-entrained concrete should have a magnesium surface. Take care not to overwork the concrete, because this will result in a less durable surface.
©
2026
Lehal.net