How much space should there be under a home on piers or a pier-and-beam foundation?

NationwideReviewed October 2026

HUD's manufactured home standards require at least 12 inches between the bottom of the main steel frame and the ground. For site-built style floors, IRC-based codes (as adopted in Bullhead City, Arizona) keep wood joists at least 18 inches and wood girders at least 12 inches above exposed ground unless the wood is naturally durable or treated. An access opening is also required: 18 by 24 inches through a floor, or 16 by 24 inches through a wall. The gap lets air move, keeps wood and steel away from damp soil, and lets plumbers and inspectors get under the home. In flood zones the floor may need to be much higher.

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.

Sources

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General information, written in our own words from the sources listed with each answer. It is not legal, engineering, tax or financial advice. Rules change and differ by state, county and city, so confirm with the office that issues your permit before you build. Last reviewed October 2026.