I’m adding on to my house to give myself a useable garage and some extra space. Take the “I” literally; nearly all of this work I will be doing myself with help from my brother-in-law Mike!
If you want to read about this project from the start, go here.
The next thing to do is the footings. Footings are made of concrete and they provide a stable base to build upon. In my case, concrete “stem walls” (nearly five feet tall) will be placed on top of most of my footings and they need to have a stable platform to rest on.
There are several different ways to form footings. You could actually just dig a trench to the exact depth and width but I thought that would be harder and required a digging blade of just the right width and some pretty precision work. In our case, we “rough dug” the area where the footings will be placed and then formed the footings with lumber.
You can use “2 by” lumber such as a 2 x 10 to form the sides of the footing. “1 by” would also work. Both of these options are fairly expensive. In the end, I decided to use 1/2″ OSB plywood for the task. Wet concrete is heavy so care must be taken to keep these boards from bowing out on the sides. A series of wooden stakes on the outside of the forms did the trick.
For footings, extreme precision on the width and depth are not required as long as the minimums are achieved. In our case, the width was 18″ with a depth of 8″.
What does matter is making the top of the footings fairly level. This will make forming the concrete wall on top of the footing easier.
The OSB was cut into 8″ strips and then laid out around the dimension of the project. More digging by hand was required in some areas that were too high. Other areas (most of the rest of it actually) was dug out too low. Since the forms were cut to the depth of the footing, this meant that there were some gaps on the bottom. To prevent concrete from seeping out from below the forms, dirt or rocks were thrown in.
The last step was the placement of “steel”; pieces of rebar which will give the footings additional strength. These are by code to be placed 3″ from the side of the footings. Only two are required on footings less in 24″ wide. The rebar is sitting on wire “chairs” to keep them elevated during the concrete pour. Where the rebar met the footing of the existing house, 5/8″ holes were drilled and the rebar inserted. This helps to tie the two footings together.
Finally, we’re ready for the concrete! I (under)-estimated about 4.5 yards of concrete for the project. It came in under mostly because of all of the extra volume cause by the over-digging. Lucky, another yard or so was going unused on another project on the other side of town so it was sent our way. We were *still* a bit shy so three bags of 80 lb. quick-crete had to be mixed by hand to level off the last few feet of the footing.
Handling the concrete chute was a learning curve and at first we had several “pour-overs”! But we just muscled the spilled concrete back into the forms. As the pour continued, we got better at the hand signals to the driver while pushing and pulling the chute into position.
After the concrete was poured, it was skimmed to the top of the footing forms. Before it hardened too much, additional rebar was driven in vertically at three foot intervals. This will make a connection between the footing and the concrete stem wall which will sit on top.
Next Blog: The Concrete Stem Walls