Rebar, short for reinforcing bar, is a long, knobby steel bar used to provide a flexible skeleton for concrete. Concrete is very resistant to compression but crumbles when it sways. Rebar helps concrete hold together when it is subjected to these lateral forces. The footing is the part of a foundation buried deepest in the ground. The foundation rests on a footing. A footing literally traces the footprint of a building. Even concrete slab foundations are surrounded by a footing.
Excavate a rectangular trench, or series of trenches, according to the approved building plan for the building you are constructing. At the least, the footing you will pour in the trench must extend below the frost line and it must be deep and wide enough to prevent the building from moving. Loose soils require bigger footings.
Lay bricks or "chairs" in the trench to support the rebar. Chairs are plastic supports made to cradle rebar. Lay the supports so all rebar is covered by at least three inches of concrete. Separate these brick or plastic supports by no more than eight feet.
Lay #5, 5/8 inch diameter rebar on the bricks or chairs. If the trench is longer than the standard length of rebar, 20 feet, then lengths of rebar must be overlapped and tied together with rebar wire.
Overlap all rebar used in footings by at least 60 times the diameter of the rebar. Overlap #5 rebar by 38 inches.
Tie overlapping sections of rebar together with rebar wire spaced every four inches. Tie horizontal sections of rebar to vertical sections of rebar where the horizontal and vertical sections cross. Wrap rebar wire around both pieces of joined rebar and tighten using a rebar wire tool.
Lay rebar around corners by bending the rebar -- and not by cutting. Never place a rebar end in a corner. Bend rebar with a rebar bender.
Drive vertical sections of rebar into the ground with a sledge hammer in most areas. Depending on the size of the building and your local building code, some vertical sections of rebar may have to be set in wet concrete. All vertical sections of rebar must be covered by at least three inches of concrete.
Tie vertical and horizontal rebar sections together with rebar wire using a rebar wire tool.
Create a three-dimensional grid of all rebar. Rebar in any horizontal plane must be crossed and tied at a 90-degree angle by another piece of rebar every six inches in a footer. Rebar in any vertical plane must follow the same rule.
Get official approval of the rebar installation in the trench before installing forms in the trench. Forms are wooden, plastic or metal barriers that restrain the flow of concrete. The horizontal and vertical grids of rebar must conform to the specifications in the approved building plan.