How to Dig Piers for Deck

Call or visit the building department in the county in which you reside to obtain the proper permits for constructing the deck. At the same time get a copy of the required building codes, since they specify how deep the frost line is in your area and, thus, how deep to dig the piers.

Install two wooden stakes directly next to the home to designate the width of the deck. Measure out from each stake to the desired length of the deck. Drive a wooden stake into the soil at each location using a hammer.

Wrap string around all four stakes and ensure they are even with a carpenter’s level.

Walk to the side of the string furthest from the home, which is where the piers will reside, and draw circles on the ground at evenly-spaced intervals along it using the spray chalk. You will need at least four piers, but may require more depending on the size of your deck. Extend the diameter of the hole to a minimum of 12 inches and up to a maximum of 24 inches, depending on the diameter of pier you are installing.

Dig each hole using a post digger tool until you reach the depth required by your building codes. If your soil is compacted tightly or the pier holes are deeper than 3 to 4 feet, rent a soil auger at a tool supply company. Wear protective eye wear when digging the holes with the auger.

Install cardboard builder's tubes in each hole, which provides a form to create the lower concrete portion of the piers.