How to Lay a Patio Foundation

Spray paint the perimeter of the patio onto the ground.

Excavate the ground inside the spray-painted lines. You can either do this by hand, or use a 1 1/2-ton excavator. Dig deep enough to go beneath the frost line. It can range from a few inches in the southern U.S. to several feet in the northern U.S., so contact your local zoning board to learn how deep the frost line is in your area.

Grade the soil in the bottom of the hole to lead away from the house and tamp it down to compact it. When grading the soil, use a slope of about 1 inch for every 12 inches of length.

Construct a wooden frame around the perimeter of the hole by driving wooden stakes into the ground around the edge of the hole every 3 feet and nailing 2-by-4 boards to them.

Cover the soil inside the hole with a vapor barrier. This is a plastic sheet that prevents water from seeping up from the ground and damaging the foundation.

Place expansion strips inside the hole along the foundation of the house. These provide a buffer between the patio foundation and the house foundation.

Pour a 2-inch layer of crushed granite or limestone into the hole. Spray it with a hose to reduce dust, then tamp it down. For larger patios, you may want to rent a mechanical plate compactor. Add two more layers of crushed rock, using the same method. Again, refer to your local zoning board for the precise requirements you must follow as it varies by location.