The Typical Footing For a Garage

Site Prep

• Before breaking ground, the contractor determines the elevation of the top of the stem wall and stakes out the exact location of the structure. Local building authorities usually request a copy of the plans for their files before they will issue a permit. Most will also inspect the site. Notify local utility companies that you plan to dig so they can check to ensure that you won't hit their lines. For new construction, the electric company will install temporary service to run power equipment.

Excavation

• The depth of the footings is determined by the final elevation of the stem wall and the local frost line. For example, if a building inspector determines that the top of the garage stem wall should be 1 foot above the current soil surface and the frost line in your region is 2 feet deep, the excavation contractor should dig the wall trenches 4 feet below the elevation line. That allows for 1 foot of elevation above the ground, plus 2 feet below the soil to reach frost line. The additional 1 foot is for the footing, which must be below the frost line.

Forming

• Whether you form the footing or pour it directly into the footing trench depends upon the type of soil in your area and building codes. For clay soils that swell and heave, code might specify pouring the footing without forms. If this is the case, the excavator will dig the footing trenches to the exact width of the footings. Formed footings are the norm in areas with sandy or rocky soil. The standard footing for a garage is about 1 foot deep and 2 feet wide, although this figure varies widely.

Reinforcement

• Steel rebar, installed lengthwise and crosswise into the footing forms or trenches, is probably a code requirement. The amount of steel you must install varies from one municipality to another, and the building inspector will check to ensure that you followed the regulations before clearing you to pour. A rebar bender and cutter lets you bend the long bars into angles before positioning them in the footer forms. Rebar chairs, which are small plastic units, elevate the level of the bars to the center of the footing form.

Pouring

• You have only a small window of time in which to work before wet concrete hardens, so recruit a few knowledgeable workers. One worker runs the concrete truck chute and will position the chute over the footing trench and direct the truck driver. At least two more workers follow closely behind, leveling the wet concrete in the forms. If you’re pouring a big garage/workshop, you may need additional workers. Just before the concrete sets, the workers will insert vertical rebar poles lengthwise in the center of the footing. These poles will serve as reinforcement, tying the stem wall to the footing.