Concrete foundations provide a solid base for buildings. There are a number of types of slab foundations that contractors use based on the type of construction and building site. Concrete slab construction centres around footings poured for support. Reinforcing materials set within the concrete help prevent cracks and settling.
T-shaped concrete slab construction uses a number of concrete pours to establish the floor. (See References 1) It’s more expensive than other types of slabs, but it holds up well in all types of conditions. Common in areas where it freezes, the T-shaped footing, or spread footing, looks like an inverted “T”, which gives it the name. (See References 2) The first pour of concrete establishes a wide base below the frost line. The next concrete pour puts the narrower, vertical foundation wall in place on top of the spread footing. The top of the wall sits at ground level. During this pour, reinforcing bar, or rebar, adds extra strength to the concrete. These footings appear at various points along the perimeter. Anchors, placed in the walls, connect the third pour of concrete, which is the actual slab floor, to the T footings. To give the horizontal slab stability, a layer of gravel sets underneath it and reinforcing mesh runs through the concrete.
The concrete contractor pours monolithic slabs in one pour. First, levelled ground receives a layer of gravel. Trenches around the edge of the monolithic slab provide space for a deeper layer of concrete to help provide extra protection from breakage. Rebar is set in the deeper areas to provide reinforcement. Mesh reinforcing materials set on top of the gravel layer give the concrete in the slab extra strength. Once the preparation work is complete, the concrete pour takes place and the concrete cures before construction of the rest of the building continues. This type of concrete slab construction works well in areas that don’t freeze.
It’s possible to modify monolithic concrete construction to protect it from the effects of frost, but it only works in a building that has heat. (See References 2) A frost-protected slab-on-grade pour has rigid polystyrene insulation attached to the vertical perimeter wall. Another polystyrene sheet butts up horizontally against the bottom edge of the monolithic pour. The insulation traps the warmth from the building’s heating system and doesn’t allow it to escape.