How to Pour a Reinforced Concrete Floor
Proper site preparation is essential for a strong, smooth concrete floor. If the site is not properly prepared, reinforcing the concrete will be only partially effective. Reinforcing a concrete floor before the concrete is poured is otherwise a straightforward job.
- Difficulty:
- Moderate
Instructions
Things You'll Need
- Mason's line Wood stakes Measuring tape Shovel Line level 40 duplex nails (double-headed nails) 2x4s Gravel Tamper Melded wire mesh or Rebar (reinforcing bar) Chairs to support the mesh Mixed wet concrete Rakes Screeding board Bull float Hand float Edger Groover Polyurethane sheet Steel trowel
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1
Mark the site and excavate to the necessary depth.
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2
Place the boards for the form. Buttress them with as many stakes as needed.
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3
Tamp down the subsoil. Add a layer of gravel or recycled concrete and tamp it down. This base should be compacted and hard, with a smooth surface that has the same grade you desire for the finished concrete floor.
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4
Choose the reinforcement best suited to the job. The most commonly used reinforcement for floors is a welded wire mesh, which controls cracking after the concrete has cured and throughout the life of the floor. Typically, this mesh has six-inch squares. It can be purchased in 5 by 8 foot sheets or in 5 by 50 foot rolls. Reinforcing steel rods, or rebar, is used for floors that will carry a heavier load.
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5
Place the reinforcement. Wire mesh should cover the entire surface of the floor site, with gaps of two or three inches around the perimeter so that it does not touch the forms. If you are planning to have control joints in the floor, leave a gap of several inches where the joints will be located. If you have to use two or more widths of mesh to cover the space, be sure to overlap the mesh edges by about six inches.
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6
Place wire mesh at a height that will be about midway in the slab. If it is too near the base or too near the surface, it will be quite useless. The simplest way to do this is to have the mesh in place before the concrete is delivered. Have the driver discharge a small bead of concrete while moving the chute in a zigzag pattern. Lift the mesh up to the top of the concrete bead, and adjust it up or down until it is at a height equal to half the final slab thickness--for instance, two inches off the ground for a four-inch slab.
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7
If you are using reinforcing bar instead of wire mesh, place the rebar in a grid pattern, with each square about 18 by 18 inches. Overlap the ends of the bar by 12 inches and wire them together. Leave two or three inch gaps around the perimeter and for any planned control joints. The grid should be raised off the ground by two-inch concrete blocks, sometimes called chairs. Don't use brick for the chairs, because they will absorb water from the wet concrete and cause a weak spot in the floor.
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8
Pour, rake, and screed the floor as you would any other concrete floor.
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9
Float the surface of the concrete.
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10
When the concrete is partially hardened, use the edger to create a smooth, rounded edge along the perimeter.
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11
Use the groover to create control joints. They should be about one-fourth as deep as the thickness of the slab.
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12
Smooth the marks left by edging and jointing with a hand float. Then smooth the surface with a steel trowel.
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13
Cure the concrete. Cover the entire surface with a sheet of polyurethane, so that it dries slowly. If the nights are cold, add a layer of loose straw on top of the plastic. Keep the concrete damp for three or four days.
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14
Remove the polyurethane sheet and the forms. You can walk on the floor now, but avoid heavy loads for a while--28 days, if possible. That is how long it takes for concrete to cure completely and reach its maximum strength.
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1
Tips & Warnings
Wear heavy rubber boots and work gloves when handling concrete. Rinse your skin with vinegar at the end of the work period to neutralize the alkalinity of the concrete. If the floor will bear heavy loads, for example, a garage floor, you may choose to use reinforcing bars instead of mesh, since rebar increases structural strength.
If you get wet concrete on your skin, wash it off promptly.
