|A typical foundation wall has 2 major components - a footing and a stemwall. These components are made up of 2 sub-components - concrete and rebar. The rebar allows the concrete wall to resist shear and bending from soil movement and wind conditions on the structure above.||
A typical footing form
The first thing you have to do is dig an area out that is below the frostline for your footing to sit on. You should then grade it level and compact it with a plate compactor or "jumping jack", which can be rented for around $25-$40 per day.
Forming the concrete footing is typically done with 2x8's, which are only 7.25" wide. This is not a problem, because I usually want it a little above the ground to enable me to easily level the top of the formwork without having to dig after I have compacted the area.
You are now ready to pour the concrete into your formwork. To figure how much concrete to order you can use the Foundation Calculator on this site or do it by hand. When doing it by hand you multiply the width by the height and then by the length of the footing (use measurements of feet, so 8" would be .666 feet). This will give you cubic feet, but we need cubic yards; so divide the number by 27, which is the amount of cubic feet in a cubic yard. This number is called a neatline quantity, but we all know that formwork is not neat. We will want to add a factor of waste into this so we don't come up short in our pour. Typically the factor of waste for pouring against the ground is 12% and pouring against formwork (stem wall) is 8%. Our footing is in contact with the ground so we will take a final cubic yardage and multiply by 1.12 to get our final order quantity.
Pouring the concrete is the final step in the process of creating a footing. Some poeple hate pouring concrete, but I think it's pretty fun. It is hard work though, so have plenty of water on hand. When pouring the concrete into the footing, don't put too much in one spot, try to keep it even throughout the pour. After you have some poured have one person go back and start "screeding" the concrete. You can do this with a 24" length of 2x4. Place it on each side of the formwork and move it back and forth, perpendicular to the formwork, and pull it parallel to the formwork at the same time. This will start the process of getting alot of the air out of the concrete, which will weaken it. You should also tap on the sides of the formwork as you go to further remove air entrapped in the concrete. When you are done screeding you should have concrete that looks like icing on a cake after you run a knife over it. Not perfectly smooth, but flat. Many people won't trowel a footing, because they think it's wasting time. It may waste some time but it makes it a lot nicer later on when we go to put our stem wall formwork together. Troweling a footing is quick; just run the trowel over it a couple of times on the outside 6" to where it is smooth, not perfect. Now you're complete with your concrete pour.
Some structural plans will require a keyway between the footing and stemwall. This is easily created by taking a 2x4 on edge and "screeding" in a 2" deep keyway into the top of the footing. This will give a much stronger connection between the footing and stemwall to help with larger shear values across the footing. In the next step of placing the vertical rebar into the footing you can place them right in the middle of the keyway.
The lengths of rebar you cut earlier now need to be placed in the center of the footing, or what will eventually be the center of your stem wall. When putting this rebar in don't "stab" it in, move it up and down so it will consolidate around the rebar. If you stab it in you will end up with voids around the rebar and it will be loose when the concrete sets up, which doesn't do any good. Place these at around 4' apart with one about 6"-12" from each corner.
The next day you should remove the spreaders and get ready to start placing your formwork for your stemwall. Some people also remove the formwork from around the stemwall, but I like to keep it there until after the stemwall is complete. This allows you to nail a 2x6 into the 2x8 formwork to hold it in place instead of trying to nail into concrete.