How to Make a Deck Footer Base

Determine the frost line in your area. The frost line is the depth to which the ground freezes during the winter months. This depth changes from place to place and is available through the building inspections authority in your area. Make a hole 6 inches deeper than the frost line and about 9 inches wide at the opening using your post hole digger and shovel. Ideally, the bottom 6 inches or so of the hole will be about twice as wide. This extra width allows the downward force of your deck to disperse over a wider area and lessens the load on the soil directly beneath your footers.

Slide your 8-inch in diameter building tube into the hole. The tube should fit snugly in the hole so that it remains suspended above the 6-inch wider area at the bottom, about 6 inches above ground level at the top. Fill in the spaces on all sides of the tube with dirt excavated from the hole using your shovel and your hands. Filter out as many rocks as possible. Check that the top edges of the building tube are plumb using your level, and adjust as necessary.

Pour concrete into the top of the tube until it fills the void at the bottom of the footer, and the entire tube until it reaches the top rim. Allow the concrete to dry and set according to the manufacturer's instructions. This process can take up to one week. Once dry, cut and peel away any visible portion of the building tube using a razor knife so that only concrete remains.

Make a pilot hole into the top of your deck footer at the very center using your hammer drill. Insert an expanding anchor bolt into the hole, and place a metal post base plate over it. Tighten it in place with your impact wrench. The bolt will anchor itself into the concrete, and provide a sturdy base for the metal post base and the post itself.

Insert a 4-by-4 pressure treated deck post into the post base anchor at the top of your footer. Drill pilot holes through the post to match the screw hole locations on your mounting plate. Fasten the post in place with your ratchet set.