Raised Patio: Footings

Tuesday was the day to get the footings done. That means the trench was finished and my dad leveled it, added a few boards as forms and we started pour concrete. But first things first - what's a footing? A footing is a small (~10" wide) , thin (~4" thick) slab of concrete that supports a wall above it. Kind of like a sidewalk, but it has to be put under ground on undisturbed soil. In places like here, (Southern Ontario), it has to be undisturbed soil that is beneath the frost line, so 3 to 4 feet down. This is to prevent the footing from shifting or buckling. Footings can be, as in this case, poured directly onto undisturbed soil inside a form. The form here consisted of planks on onside of the trench, with the other side chopped straight, the soil forming the side. The footing will be buried so finish is not important.

As you can see in these pictures, part of the problem with building this deck is that the footing needs to go right up against the existing wall. The ground near the house is back-filled and has not yet had the necessary amount of time to settle. Excavating within about 5' of the house meant that we were not on undisturbed soil. To counter-act this problem, 2 holes (3-4 inches deep - about half the thickness of the basement wall) were drilled in each section that met the house. Into each hole went an 8 foot long piece of rebar. This effectively ties the footing to the house, so any movement has to move the house and the footing together. Note that this is not a challenge, as I like the house and footing where they are.

The pictures also show some of the footing. To pour the footing to this point required about 2/3 of a cubic yard of concrete. My dad and I mixed the concrete and brought it on-site. This resulted in a vast monetary savings and a lot of work. A yard of concrete, from a company like CBM or Lafarge, would cost about $400 delivered. The cost of the materials in this case was about $40 of aggregate and gravel and $100 of cement, although that last number is probably high. However, we did have to shovel the gravel into the mixer and then from a box into the trench. The weight of 1 cubic yard of concrete is about 2400 kg, so this was about 1600 kg. Shoveled twice. But cheaper than the big spin-y truck.

We ran into problems when we got the concrete on site - it was hardening quicker than expected and was difficult to shovel. As in it was almost one solid mass. The pickaxe did the trick however and loosened it sufficiently.

Also present are some concrete blocks, sometimes known as "cinder blocks", but in this case 8" standard concrete blocks and 8" split-face blocks. The split-face blocks are what will form the walls above the ground on the outside. Other, older, left-over 8" blocks will be used below ground.

That's all the pictures I have right now, but tomorrow I will take pictures of the finished footing, the extra blocks and the pile of brick-sand. Tomorrow is when the blocks start getting laid.