How to Pour and Set Concrete Footings for Deck Posts

FOOTINGS are the literal foundation of your deck, acting as the bridge between the structural load of your house extension and the earth beneath it. If your footings move, settle, or heave, the entire deck follows suit, leading to sagging beams and unstable railing. A job well done means a flat, level, and rock-solid base that stays locked in place through winter freezes and summer droughts. Getting this right requires more labor than technical genius. You must reach the load-bearing soil, typically below the frost line in your region, to ensure the concrete doesn't shift. When you finish, your deck posts should sit on hardware that keeps them elevated above the concrete surface, preventing rot and moisture buildup. Focus on the depth and the plumb of your forms, and the rest is just muscle.

1. Dig Deep and Level. Mark the exact center of your post locations using stakes and string lines. Dig your holes at least 12 inches wide and deep enough to reach your local frost line requirement.
2. Set Your Forms Plumb. Cut your cardboard deck pier forms to length so they sit level with each other. Place them in the holes and verify their position against your string lines.
3. Nail the Level. Use a long level resting across your form tubes to ensure they are at the same elevation. Adjust the height by trimming the cardboard if necessary.
4. Get the Consistency Right. Mix your high-strength concrete in a wheelbarrow or portable mixer according to the bag instructions. Aim for a consistency like thick oatmeal—not too runny, not too dry.
5. Pour Without Air Pockets. Fill the forms to the top. Use a scrap piece of lumber or a mechanical vibrator to poke the concrete and remove air pockets as you pour.
6. Lock in the Hardware. Smooth the top with a trowel, then press your post base hardware into the wet concrete. Use a level to ensure the bracket is perfectly vertical.