Column footing size for a 3-story (G+2) building: The general thumb rule for a 3-story (G+2) house or a simple 3-story building is that the recommended size of the column footing should be 5' x 5' x 5' (1.5m x 1.5m x 1.5m) for isolated footing shallow foundation in gravel and sand soil with higher bearing... The general thumb rule for a 3-story (G+2) house or a simple 3-story building is that the recommended size of the column footing should be 5' x 5' x 5' (1.5m x 1.5m x 1.5m) for isolated footing shallow foundation in gravel and sand soil with higher bearing capacity such as clay or loam. For lower bearing soils, such as coarse sand or compacted dirt, you can use footings that are 4' x 4' x 4' (1.2m x 1.2m x 1.2m). It's important to remember that larger footings will usually result in a stronger foundation. As long as you follow the proper procedures when putting a shallow foundation into place, you should have no problems with it holding a house up. But just like any other part of a home, if you want it to last forever, you need to take care of it. Keep reading below for more information on footing sizes for different types of buildings.