Definition
A foundation is the structural element that transfers building loads to the ground. Foundations distribute weight to prevent settling or failure. Common types include slab-on-grade (for warm climates), full basement (providing living space), crawl space (elevated floors), and pier foundations (for difficult soils or slopes). Foundation depth must extend below the frost line to prevent heaving from freeze-thaw cycles.
Formula
Foundations must extend below the local frost line to prevent damage. Frost lines vary from 0 inches in Florida to 60+ inches in northern states. Contact local building authorities for specific frost depth requirements in your area. Footings must also bear on undisturbed soil at the proper depth.
Example
Foundation Selection Example
In Minnesota with a 42-inch frost line, a basement foundation typically extends 8 feet below grade, with footings at the bottom of foundation walls. In Texas with a 12-inch frost line, a slab-on-grade foundation is common. For sloped lots, a walkout basement or pier foundation may be more cost-effective.