How to Extend an Existing Concrete Spread and Footing

Determine how deep you need your footing to be. The depth depends on the type of soil you have. You'll need a depth of at least 4 inches, says Philip Schmidt in "The Complete Guide to Patios." If you hit any soft spots in the soil, you may need to excavate further until you reach solid ground. Excavate the area at least 10 inches wider than the spread.

Prepare the excavated area by pressing down the soil with a tamper to make the ground more solid. Then pour gravel into the excavated area, filling it to the top. Use a gravel compactor to firmly pack down the gravel, so it won't sink much.

Place three of the two-by-four pieces of lumber around the perimeter of the area where you will lay the concrete. The wood will define the shape of the concrete. Tamp stakes into the ground behind the two-by-fours to hold them in place.

Pour in your concrete after preparing it according to the directions. Level off the top with a forth two-by-four, which must be wider than the concrete area. Lay it flat at the point where the existing concrete surface meets the newly poured concrete, and slide it outward to scrape off excess concrete and flatten the surface.

Use an edger to subtly round the edges of the concrete form. If the existing concrete surface has texture, add texture to the new surface by scraping a rough broom over its surface. Then cover the concrete area in plastic and mist the surface each day for two weeks, not putting weight on it until the end of that time. Then lay soil over the surrounding gravel footing and replant it with grass or flowers.