AR · set by county and city amendment
How deep do deck footings and fence posts have to go in Arkansas? Below the frost line. Here's the number, and the winter behind it.
The requirement
12″
Footing bottoms in Arkansas must reach 12 inches below grade — the frost line. Across Arkansas it runs roughly 12″–18″ by county.
Reference: 2021 Arkansas Fire Prevention Code, Volume III (Residential), Section R403.1.4 and Table R301.2(1) (2021 edition). Counties amend their codes — confirm the exact figure with your local building department before you pour.
Depth pre-filled to the Arkansas frost line. The hole bottom has to reach it — a few inches deeper seats the base cleanly below.
| 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.
Arkansas winters bring regular but brief freezes, so the ground typically freezes only a few inches to about a foot. Frost penetrates somewhat deeper in the higher, colder Ozark and Ouachita country in the north and west.
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.
The state adopts an IRC-based residential code, but each jurisdiction fills in its own frost depth; Little Rock, Fort Smith, and Fayetteville all list 12 inches. Northern Ozark highland jurisdictions run closer to 18 inches, and footings must always reach at least 12 inches below undisturbed grade.
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.
12 inches is the working number (set by county and city amendment). Across Arkansas it runs roughly 12″–18″ by county. Confirm the exact figure with your local building department — county amendments are common.
Bury one third of the above-grade height, never less than 24″, and never shallower than the frost line — in Arkansas that means at least 24″. The post depth calculator checks both rules for you.
Below the frost line — 12″ minimum, bearing on undisturbed soil beneath it. Size the diameter with the deck footing calculator, then figure bags with the depth pre-filled above.
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.