[header] How to build a concrete foundation [title] Choose the type of foundation to build. [step] The type of foundation depends on the area of the foundation will be located on and the type of structure that will be placed on it. [substeps] Shallow foundations are built on level ground and hard surfaces. 
Shallow foundations are no more than 3 feet (91.44 cm) deep and are used primarily for smaller, simpler projects like holding patio furniture, a fountain, or an air conditioning unit. Deep foundations are used for more complex projects.