How much should the ground slope away from the home?
NationwideReviewed October 2026
The common code rule is at least 6 inches of fall within the first 10 feet away from the foundation. That figure comes from the International Residential Code (section R401.3), as adopted in local codes such as Bullhead City, Arizona and Massachusetts. HUD's manufactured home installation standards state a similar rule: a minimum of one-half inch per foot away from the foundation for the first 10 feet, with drainage diverted so water does not pool or erode under the home. Where lot lines or other features prevent that much fall, IRC-based codes generally allow swales or other approved methods to carry water away. Water collecting under a raised home softens soil, rusts steel and feeds mold, so grading matters as much as the piers.
Check your local rule. This varies by state, county or city. Your permitting office has the final word; the official lookup pages below show you who that is.