Pouring a concrete pad is an affordable and efficient way to install a strong, flat surface for a patio, walkway, shed or other structure. Preparing to pour a concrete pad involves laying a base and building a frame to ensure the pad has adequate support and drainage. When poured, concrete is in a thick, semi-liquid form that will take the shape of the frame in which you pour it.
Excavate the site for the slab, digging an 8-inch-deep recess in the ground. Level the area by digging out high spots and compact the soil with a compactor machine to squeeze out air pockets.
Assemble 2-by-4-inch pressure-treated boards against the interior sides of the recess to form a box frame, with the 2-inch side on the bottom. Set additional boards directly on top so that the frame is the height of two boards, in order to cover the 8-inch-deep walls. Screw the boards together with 2½-inch screws and a drill. Brace the frame by inserting 1-by-3 inch garden stakes along the outside of the boards and in the corners.
Pour 4 inches of aggregate and rake it evenly over the bottom of the recess. Compact the aggregate until the surface is hard and flat.
Lay wire mesh over the top to reinforce the concrete. If you're pouring a large pad, lay rebar near the ends and through the center.
Dampen the aggregate when you are ready to pour the concrete pad to help it adhere to the base.