VT · statewide code figure
How deep do deck footings and fence posts have to go in Vermont? Below the frost line. Here's the number, and the winter behind it.
The requirement
60″
Footing bottoms in Vermont must reach 60 inches below grade — the frost line. Across Vermont it runs roughly 48″–72″ by county.
Reference: Vermont Fire and Building Safety Code (2015 edition), amended IBC Section 1809.5 — foundations must extend below the local frost line and not less than 5 feet (60 inches) below finished grade (2015 edition). Counties amend their codes — confirm the exact figure with your local building department before you pour.
Depth pre-filled to the Vermont frost line. The hole bottom has to reach it — a few inches deeper seats the base cleanly below.
| Bag size | Exact | Buy (with spare) |
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The buy column adds a 10% spare margin and rounds up. Running out mid-pour is the one mistake you can't fix.
Vermont's long New England winters keep the ground frozen for months on end, and frost routinely reaches four to five feet. Penetration is deepest in the far north and at elevation, where snow-free, exposed ground freezes hardest.
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 60-inch state minimum applies to buildings regulated under the Vermont Fire and Building Safety Code (a 2025 edition has since been issued); detached single-family homes are lightly regulated in many towns, but builders use the same depth. Cold hollows and the Northeast Kingdom can require more than 60 inches; southern valleys commonly see 48 inches.
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.
60 inches is the working number (statewide code figure). Across Vermont it runs roughly 48″–72″ 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 Vermont that means at least 60″. The post depth calculator checks both rules for you.
Below the frost line — 60″ 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.