How to Place Rebar in Concrete

Drive short pieces of No. 4 rebar vertically into the ground about every 16 inches around the future concrete slab's perimeter, placing each at least 3 to 4 inches from the future slab's edge. Each piece needs to extend about 6 inches below ground and about one-half the height of the future concrete slab above ground. Using a hammer or small sledge hammer will help you drive the rebar pieces, which will be anchor posts. If you need to cut the rebar, use a table saw and metal cutting blade.

Cut lengths of rebar to run across the slab location from one rebar anchor post to another rebar anchor post. Use tie wire to fasten each length of rebar to its respective anchor posts and to any other lengths of rebar that intersect it as part of the grid pattern. Twist the tie wire around each piece of rebar tightly several times to form a secure joint. Use wire snips to cut off excess wire.

Place 2-by-2 inch concrete blocks, which are called dobies, beneath each plus-shaped (+) joint formed by two intersecting pieces of rebar. Install as many of the concrete blocks as necessary beneath each joint to bring the support to the level of the rebar. These small supports help to hold the rebar at the proper height and prevent sagging and movement.

Put on work gloves and eye goggles for protection. Wet concrete is corrosive and can cause skin irritation. Prepare a concrete mix according to its manufacturer's package directions, and pour the resulting wet concrete over the grid of rebar. Allow the concrete to dry and set according to its manufacturer's instructions.