How to Make a Strong Footing for a Support Post

Dig a hole with a shovel that is at least 10 percent larger than your proposed footing and that is at least 32 inches deep. It should also be at least 1 foot deeper than the "frost line" or the depth of the deepest recorded frost in your location. Measure the dimension and depth of the footing with a steel measuring tape.

Compact the soil on the bottom on the bottom of the hole with a tamper.

Cut an 8-foot-long length of 1-by-10-inch board into four 20-inch-long pieces and four 3-inch-wide strips with a circular saw. The 3-inch strips will act as "cleats" to which other boards can be nailed to create a concrete "form."

Nail the 3-inch wide strips flush to both ends of two of the 20-inch-long pieces using four penny common nails and a claw hammer. Nail both strips to the same side of each board.

Nail all four boards together to form a square using four penny common nails and a claw hammer. Nail the boards without attached wood strips to the boards with strips on the end. This concrete form does not have to be perfectly square.

Cut a 4-foot length of No. 5, 5/8-inch-diameter rebar into four 12-inch-long pieces using a hacksaw.

Lay the concrete form made of 1-by-10-inch boards in bottom of the hole. Lay four bricks inside the form so they form a rough square and no brick is closer then 4 inches from the form.

Lay two sections of the cut rebar on two bricks each to form two parallel lines. Lay the remaining pieces of cut rebar across the first two pieces of rebar at right angles to form a grid. Tie all four pieces of rebar together with rebar wire.

Mix half a bag, about 50 lbs. of Portland cement, two 50-lb. bags of sand, 150 lbs. of 3/4-inch-diameter gravel and 3 gallons of water in a portable cement mixer until the mixture achieves the consistency of wet clay. If the mixture clumps, add more water.

Shovel this concrete into the form until the form is completely filled. Depending on the weather and how much water you use, you may have up to 1/2 cubic foot of concrete left over.

Level the top of the formed concrete with a 1-foot piece of scrap lumber. Cover the form with a large, plastic trash bag.

Disassemble and remove the form after three days. Allow the footing to cure for at least 10 days before installing your support post.