Glen & Kris Denning → Home Improvement → Deck < Previous Next >
This series of pictures show how the sonotubes for our deck were installed.
The first picture shows a hole 26" in diameter and 56" - 58" deep. About 17 cubic feet of dirt was removed to create each hole. The dirt was a mixture of very hard clay and large rocks (some as big as a football). We used a rotary hammer to break up the clay so we could remove it from the hole. Local code requires deck footings to be at least 50" deep so that they are below the frostline. Once the holes were finished, we lined the bottoms with Typar, then compacted 6" of gravel as a base for the footings. Also evident here is a grid of ½" rebar that reinforces the footings.
The second picture shows an 8" sonotube attached to a Bigfoot Systems BF24 high-density polyethylene (HDPE) footing form. The Bigfoot and sonotube were assembled as a unit, then lowered into the hole over the rebar grid shown in the previous picture. Since we had to dig large holes anyway, it seemed reasonable to use the Bigfoots for a number of reasons. Unlike wood, the HDPE form remains in place after the footing is poured. The large footprint offers good load-bearing properties in our poor soil conditions. Finally, the shape and large size also offers a high resistance to frost jacking, especially important since the deck isn't attached to the house.
The third picture shows sonotubes placed in the eight holes. Kris and I dug four holes apiece, and each one took us 10 hours to complete. We finished the excavation in a five-day period, including transporting the 5 cubic yards of dirt we removed from the holes to a commercial disposal site.
Once the sonotubes were placed in the holes, we secured the tops of the sonotubes with batter boards and metal stakes to prevent them from shifting during the remaining operations. Next, we back-filled the holes with clean, non-freezing fill. Then I used a laser–level to mark each sonotube and cut them to finished height.
We rented a concrete mixer and poured 3½ cubic feet of concrete into each sonotube and footing. Two pieces of ½" rebar reinforce each sonotube vertically, and 5/8" x 8" J-bolts placed in the wet concrete were used to secure the beam brackets.
Next, we install the beams and joists.