When building a concrete porch or a sidewalk, the concrete is poured in a liquid form, then sets over a period of a few days. To keep the concrete from flowing all over the place, a formwork needs to be put in place to hold the concrete while it cures. Improperly installed formwork will cause the concrete to cure improperly, look crooked and ruin the job. As in most DIY projects, preparation is the key to a good finished project.
Measure out the length and the width of your concrete slab area.
Cut a 2-inch by 12-inch board that is equal to the length of one side of your intended concrete area.
Pound two 2-inch by 4-inch stakes into the ground in the corner of the intended slab area. Nail the 2-by-12 to the two stakes.
Set up a builder's level and use it to level the 2-by-12.
Place 2-by-4 stakes every 2 feet along the board to brace the 2-by-12.
Cut a second 2-by-12 to the width of the concrete slab. Nail one end to the other 2-by-12 end. Calculate the diagonal for 90 degrees and run a measuring tape from one end of both 2-by-12s to make sure the form is straight.
Add the other two sides of the formwork in the same manner.