You have a nice spot in the yard for a patio, or want to build a garage or storage shed. No matter how big or small the project, the first step is to excavate for a concrete slab. If you don't mind some hard work, you can excavate yourself. Once you plan and measure everything, grab a shovel and start excavating.
Check your local ordinances for building outdoor structures. You may be limited as far as size, placement or type of structure. Make sure you are within ordnance laws before purchasing materials.
Measure out the area for the concrete slab. Shape by placing stakes in the four corners of the area and forming square with string. Check area for square by measuring from one corner diagonally to the other corner. Adjust position of stakes, if necessary.
Shovel down 10 inches-6 inches for gravel and 4 inches for thickness of the concrete slab. Remove rocks and large roots to leave the bottom of the excavated site as smooth as possible. For water runoff, pitch ground 1/4 inch for every foot. Slope away from the house or other outdoor structures.
Use 2-by-10 inch boards to build a form, which holds the gravel and concrete slab in place. Pour in 6 inches of gravel, and tamp down. Smooth out gravel to make a level surface, allowing enough space for the concrete slab to be level with top of the area you want to excavate.
Install 1/2-inch steel bars to form a reinforcing grid for the concrete. You can lay large flat rocks beneath the middle of the grid for additional support.
Place bars every 2 feet from the sides, back and front of the excavated area. Tie where the bars intersect with wiring.