To pour a concrete garage floor, build forms on a level area, pack the ground underneath, set steel bars to reinforce the concrete, and pour the concrete into the form. Preparing the site is the most important step in the process. Dig down several inches, trying to make the ground as level as possible. Add gravel to the area, and compact it down, striving to create as level a surface as possible.
Once the site has been prepared, build strong, level forms out of wood to contain the concrete once it is poured. Build braces on the outside of the forms to help to keep them upright and create straight sides to your floor. If the weather is hot and dry, divide the floor into two halves and pour them on different days.
Install steel reinforcement bar in the area where the concrete is going to be poured. Wire the perimeter of the floor, and then create a grid pattern at four foot intervals.
Start pouring the concrete into the form. Using a straight 2-by-4-inch screed board, flatten the top of the concrete. Finally, use a trowel to smooth out the top layer of concrete and to create a small separation between the concrete and the forms.