A fast and easy method of installing deck footings or piers is made possible by pouring concrete into a cylindrical cardboard form. The forms are available under several brand names but look and function the same way. That part of the deck frame which is not bolted to the main foundation wall is supported by wooden posts; each post bears on a separate concrete footing. Deck posts are typically either 4 x 4 or 6 x 6 inches in nominal dimensions. The cylindrical concrete footing is poured to a height just above the grade and extends down below the frost line. The base of each post is secured to a bracket which is anchored to the top of the footing. You can install cylindrical concrete footings for your deck by following the simple steps below.
Step 1 - Dig the Hole
The first step is to dig the hole for the form. Use a post hole digger to dig a hole deep enough to penetrate the frost line. Footings 12 inches in diameter will be sufficient for deck supports. Fill the bottom of the hole with 6 inches of gravel to divert water from the footing.
Step 2 - Prepare the Form and Set it in Place
You’re going to bring the footing to a height 2 to 4 inches above the grade. You can use a circular saw to cut the cylindrical cardboard form to size. The form should be coated with a form-release compound or ordinary motor oil so that it is easily removed when the concrete has set. Place the form in the hole and backfill around the form. Make sure that the form stands plumb by placing a level on the top of the cylinder. Also, make the tops of all the forms level with each other so that the deck itself will be level.
Step 3 - Pour the Concrete and Install the Anchor Bolt
You can estimate the total amount of concrete needed by multiplying the circular area by the height of each form. Concrete can be purchased as a pre-mixed, ready-to-use product that requires only adding water. Pour the concrete mix into the form level with the top of the cylinder. Place an anchor bolt 6 inches long in the center of the concrete extending about an inch above the top surface of the footing. The concrete will reach its final set after 7 days, after which time you can remove the cardboard form from the above ground, exposed section of the concrete footing.
Step 4 - Install the Brackets
Obtain a U-shaped galvanized steel bracket for each footing, sized to fit onto the base of each post. When the concrete has set, fasten the bracket onto the anchor bolt with a nut and a washer. The post will be secured to the bracket with #8 galvanized nails nailed through perforations on each side of the bracket.