How to Lay a Four-Inch Concrete Slab
- 1). Drive wooden stakes into the ground or use spray paint to mark the perimeter of the slab.
- 2). Excavate the area inside the paint or stakes, digging beneath the frost line to prevent the slab from being damaged by upheaval when the ground freezes and thaws. Your local zoning board can provide you with the required depth. For a small slab, you can dig with shovels, but for a larger slab, you may want to rent a 1 1/2-ton excavator.
- 3). Build a frame for the slab by driving wooden stakes into the ground around the perimeter of the hole and nailing two-by-four boards to them. If desired, you can apply a light coating of motor oil to the inside of the frame, which makes removal easier. (Take care not to spill any into the soil.)
- 4). Lay a vapor barrier on the dirt in the bottom of the pit. This is a plastic sheet that prevents moisture from seeping up through the ground and damaging the concrete.
- 5). Add a layer of sand or gravel on top of the vapor barrier, following local building codes.
- 6). Place wire mesh or rebar on the sand or gravel base, again following local building codes. This helps to strengthen the concrete.
- 7). Mix a batch of concrete, following the instructions on the packaging. Use a wheelbarrow for smaller slabs, and a concrete mixer for larger slabs.
- 8). Pour the concrete into the pit until it is slightly higher than the top of the frame.
- 9). Screed the slab to smooth the surface of the concrete and expose any low spots in the pour. To do this, drag a two-by-four across the top of the frame with a side-to-side motion (you'll need a partner's assistance). Fill in any low spots with more concrete, and screed the surface again.
- 10
Place a bull float on the edge of the concrete closer to you. With the back edge of the float in the air, push the float across the concrete. Lower the float to the surface when you reach the other side, and slowly pull it back towards you. - 11
Cover the concrete with plastic sheathing. Once a day, lift the sheathing and add enough water to keep the slab damp, then cover it back up. Continue this for a week, then allow the concrete to cure for 4 to 5 days. - 12
Lift the plastic sheet off the concrete and remove the wooden frame.
