How Do You Pour a Concrete Slab?


Quick Answer

Prior to pouring a concrete slab, prepare the area and construct appropriate level and square concrete forms. Then pour and level the concrete within the prepared forms. It's easiest to contract with a ready-mix concrete company to prepare and deliver the concrete.

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Full Answer

  1. Prepare the location

    Place wooden stakes into the ground to mark the corners of the new concrete slab, and string a line from stake to stake to identify the area. Using a string level, note the slope of the ground, then dig or add soil to flatten the space. Locations with poor drainage and clay-rich soils require leveling 6 to 8 inches of compacted gravel in preparation for concrete.

  2. Construct concrete forms

    Purchase straight 2x12 or 2x6 form boards to construct concrete forms for the slab. The wider width boards create a slab with a thick edge, while 2x6 boards are more appropriate for driveways. Join boards together using cleats when long lengths are required. Cut the end boards to the exact size of the concrete slab, and the side boards to 3 inches longer than the slab. Using double-headed nails, connect the boards, and attach bracing. Then brace the forms to ensure straight edges by driving 2x4 stakes along the outside of the forms. Verify that the constructed form is square and that corners measure 90 degrees before proceeding.

  3. Fill the base

    Spread a fill layer of gravel no more than 3 inches thick inside of the form, leaving a trench along the inside perimeter for the concrete's thickened edge. Tamp the gravel firmly using a rented plate compactor. If the project requires additional reinforcement, place steel bars along the edges of the base and in a grid pattern throughout the interior of the form.

  4. Prepare and pour the concrete

    Contract with a ready-mix concrete company to deliver the concrete for the slab, or prepare concrete according to manufacturer's directions for smaller slabs. If a ready-mix delivery is expected, plan the truck's path to the prepared site. Begin placing concrete in the part of the form furthest from the truck as concrete is quite heavy and difficult to transport more than a few feet.

  5. Level the slab

    Roughly rake the newly poured concrete, then use a straight 2x4 board to sweep across the surface leveling the slab. Follow up with a bull float, overlapping on each pass for a smooth surface. After the surface water disappears, round off edges of the slab with a slab tool for a finished appearance.

  6. Remove the form boards

    Lay plastic over the slab, or spray the newly formed slab with a curing compound during curing. Once the concrete has cured completely, usually overnight, remove the concrete forms.

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