HI · statewide code figure
How deep do footings go where the ground doesn't freeze? Down to the code minimum — here's the number and what still matters.
The requirement
12″
Hawaii has no meaningful frost depth. Footings still go at least 12″ below grade — that minimum is about solid bearing, not frost.
Reference: Hawaii State Residential Code (2018 IRC with state amendments, adopted by the State Building Code Council), Section R403.1.4 (2018 edition). Counties amend their codes — confirm the exact figure with your local building department before you pour.
Depth pre-filled to the 12″ code minimum.
| Bag size | Exact | Buy (with spare) |
|---|
The buy column adds a 10% spare margin and rounds up. Running out mid-pour is the one mistake you can't fix.
Tropical lowland temperatures never drop low enough for the ground to freeze, so the soil stays warm year-round. Freezing air occurs only near the summits of Mauna Kea and Mauna Loa, far above where anyone builds.
The depth tracks how much freezing a winter actually delivers. NOAA's Air Freezing Index keeps a running score of how far and how long air temperatures sit below freezing; deeper scores mean deeper frost, and building codes translate that climate record into the footing depth above. Water expands about 9% when it freezes — when that happens under a footing, the ground lifts it. That's frost heave, and it cracks foundations, tilts fence lines, and pops deck piers. Getting below the frost line puts your concrete where the ground never freezes.
Hawaii has no frost line at habitable elevations, but footings must still reach the code-minimum 12 inches below undisturbed grade. Each county (Honolulu, Hawaii, Maui, Kauai) amends the state code, so confirm locally.
Treat this page as the starting number, not the permit. County and city amendments are where the real precision lives, and inspectors enforce the local figure — one phone call to the building department settles it.
Effectively zero — the ground doesn't freeze deep enough to move a footing. The code minimum of 12″ below grade still applies, for bearing rather than frost.
The ⅓ rule governs: bury one third of the above-grade height, never less than 24″. A 6 ft fence wants 24″ in the ground. The post depth calculator does it in one step.
At least 12″ below grade on undisturbed soil. Size the diameter with the deck footing calculator.
Yes — 811 covers every state, and the locate is free. Call a few business days before any post hole or footing dig and crews mark the buried utilities.