Footers are the true foundation of any building. Added to a concrete slab for structural strength, footers bear the heavy loads of the structure and take the pressure off of uplifting forces that can occur during high winds. Footers are also used in conjunction with steep grades where building stem walls are a must. Footers provide the foundation for the block wall and the support reinforcement needed behind the wall as backfill is added and structural materials are added to the top.
Footer construction begins with a blueprint. Any slab bearing a load will automatically have a footer and the blueprint will detail the exact specifications required for the footer. These specifications are determined engineers and building inspectors which they determine from structural loads, environmental materials and regional building preferences.
Digging a footer is preferably done by hand, but larger footers certainly can and are dug using heavy equipment like backhoes, especially when soil conditions demand it. Hand dug footers are easy enough, once you get the right tools for the job. Excavation occurs only when the form work has been completed. Once you have a point to take measurements from (the top of the form) you can begin digging the footer.
Start first with a guide line to the width of the footer. A tape measure and your finger drag the perfect mark in the soil to follow for the first stage of rough digging. Use a round point shovel and a mattock to break up stubborn soils. Once you get the majority of the dirt out of the footer, it’s time to clean it up some.
Switch digging tools and grab a square tipped shovel. Scrap and dig the beginning of the footer out to the desired depth and width. Now you can use this flat finished spot for a reference point while digging. Now climb into the footer ditch and use your full force to slide into the adjacent soil with the shovel to remove it. Throw the excess dirt in or out of the forms as needed.
As you work your way down the length of the footer, continually check the measurement is still maintaining the proper depth and width. You can simplify this process by marking the handle of the shovel with a tape measure before hand. You can now use the handle of the shovel to quickly gauge depth and width, without having to switch tools.
Finish off the footer by gently scraping the inner edge of the footer wall that meets the slab on a 45 degree angle about half the width of the shovel head. This creates a thickened edge when concrete is poured into the slab, similar to an upside down bell shape, provided added strength to the slab and footer bond. For more information on concrete basics, check out Construct101’s free concrete page.