Acquire the proper permits in accordance with local building codes.
Measure the area for the foundation so that it is 3 inches wider than the base of the shed in all directions.
Drive stakes in the ground to mark the area for the concrete foundation.
Dig down 6 inches in the staked-out area.
Level the base of the dug-out area, removing hills and filling in valleys.
Tamp the soil to pack it down tightly with a tamper or use the end of a two-by-four.
Place 2-by-6-inch boards tightly around the inside edges of the hole to create a concrete form. The form keeps the concrete in a specific area.
Place 1-by-2-inch boards every 6 square feet across the width of the foundation to act as expansion joints. An expansion joint allows for a small amount of movement within the foundation and keeps concrete from cracking and breaking.
Pour 4 inches of crushed stone to the base of the hole, level the stone to fill in valleys and even out high spots.
Place reinforcing wire mesh on top of the crushed stone. Reinforcing wire mesh strengthens the concrete.
Order a 2,000-psi concrete pour from a ready mix concrete delivery company. Tell the concrete company the dimensions of the project so they can calculate the amount of concrete. Psi refers to the amount of weight the concrete is able to handle without breaking or cracking.
Spray water over the crushed stone immediately prior to the concrete pour.
Pour concrete into the corner of the form, moving toward the center of the foundation; do not let the reinforcing wire mesh move. Hold the reinforcing wire mesh in place with a heavy rock or cinder block, but move the anchor from the path of the flowing concrete.
Drag a bull float across the newly poured concrete surface to level and smooth it. A bull float looks like a trowel connected to a pole.
Insert a trowel between the forms and the concrete to detach the concrete from the forms in order to remove them after the concrete hardens fully.
Spray curing compound over the concrete surface, and let it dry thoroughly before installing the shed.