What is soil bearing capacity and how is it figured for a small home?

Bearing capacity is how much weight per square foot the soil can carry without sinking, given in pounds per square foot (psf). HUD's installation standards list soil classes from rock or hard pan, rated 4,000 psf or more, down to peat and organic soils that need a professional to evaluate. Installers can find the value from soil tests, local building department records, visual classification under ASTM methods, or a pocket penetrometer (a hand tool pressed into the soil). If none of these is used, the standards allow a default of 1,500 psf. The number matters because it sets how large each footing pad must be and how far apart piers can go. Soft, wet or organic soils call for an engineer.

Sources

• 24 CFR Part 3285, Model Manufactured Home Installation Standards (2020 edition)U.S. Government Publishing Office (HUD regulation)
• 24 CFR Part 3285, Manufactured Home Installation Standards (current)eCFR, Office of the Federal Register