Whether you are installing a deck or pouring a concrete foundation slab, it is important to have a strong base that won't settle into the soil. This means you will often need to dig and pour a footing for extra support. A footing is an additional structure that is attached to your post or slab to transfer the structural load from the object above to the earth. Creating a footing isn't a difficult process. To do so you will simply need to dig the hole for the footing to local building code specifications, and then fill the hole with concrete. After curing, you can continue with your building, secure in the knowledge that what you place above ground is more likely to remain there.
Mark out the locations for your footings using lawn flags to denote the centre of each. Place a footing everywhere you need to place a supported post.
Remove a flag and then dig a flared hole for each footing with a clamshell digger centred on the flag location. Check with your local building inspector for the depth necessary for your footings. All footings must run to a depth that is at least 12 inches under the level at which the soil in the area freezes. This will keep the footing from heaving during freeze/dry cycles. Create your footings at least 8-inches thick and twice the width of the post or wall that the footing supports.
Use a utility knife to cut a waxed fibre tube small enough to fit into the hole. You can purchase the tube from a home improvement store or lumberyard. Cut the tube long enough that when placed into the hole the tube top rises two inches above the surface and the tube bottom sits 12-inches above the base of the hole. Center the tube by screwing the upper end to temporary braces surrounding the hole. You can create temporary braces using 2-inch by 4-inch boards, cutting the boards with a handsaw to surround the circumference of the hole and then joining them together using screws put in place with an electric screwdriver.
Mix the concrete for the footing in a wheelbarrow by folding the dry concrete mix with water using a spade, until you reach a pourable consistency. Pour the concrete into the tube so that you fill the flared portion at the bottom with the concrete along with a two-foot section above. Stick a large wood pole into the tube and pull the pole up and down in the tube to mix the concrete slightly, removing any air bubbles contained in the poured section. Continue to fill the hole to the top of the tube, working in 2-foot sections, agitating each section after the pour. Smooth out the top using a 2-inch by 4-inch board as a screed, moving the board back and forth across the concrete.
Add rebar as required by the building code by pushing the rebar down the hole while the concrete is still wet. Use rebar long enough to extend to the bottom of the footing. Place your post base, if needed, into the wet concrete so that it hardens in place.
Cure the concrete for two days, misting it with water from a hose to maintain moistness. Remove the temporary brace and then cut away the exposed section of the tube using the utility knife.
Call the building inspector to check the depth and diameter of the footing before filling with concrete.
Tips and warnings
- Call the building inspector to check the depth and diameter of the footing before filling with concrete.