Frost depth in Maine
Maine has two code depths: 48 inches in 72 inches — and which one applies depends on the county you build in. Add 6 inches of bearing and that becomes a dig depth of 54" / 78". The numbers below are the code values an inspector measures, not climate averages — the local building department always has the final word.
| Area / zone | Frost depth | Dig depth | Set by |
|---|---|---|---|
| Southern & coastal | 48" | 54" | MUBEC (IRC) Table R301.2(1) |
| Northern & western mountains | 72" | 78" | Town Table R301.2(1) |
Two rows, two numbers: the county you build in decides which one governs your permit. Never take the shallower value to a counter in a deeper zone.
Why Maine's number looks the way it does
Maine splits New England's coldest state in two: 48 inches along the southern coast, and 72 in the northern and western mountains — tied with interior Alaska for the deepest requirement in the country.
From frost depth to dig depth in Maine
Footings bear on undisturbed soil below the frost line, so the hole goes 6 inches deeper than the code number. In Maine that means:
| Code frost depth | Dig depth | Shortest Sonotube |
|---|---|---|
| 48" | 54" | 6 ft tube |
| 72" | 78" | 8 ft tube |
A 4-inch gravel base at the bottom of the hole is common practice for drainage, and if you use one, add it to the tube length rather than the dig depth — the footing still has to reach the full 48–72 inches below grade.
How much concrete a footing takes in Maine
Bags of 80-lb mix per footing, for a solid pier with no post in the hole, at Maine's code depth:
| Frost depth | 10" hole | 12" hole | 16" hole | 20" hole |
|---|---|---|---|---|
| 48" (54" dig) | 5 bags | 6 bags | 11 bags | 17 bags |
| 72" (78" dig) | 6 bags | 9 bags | 16 bags | 24 bags |
The bags calculator converts any total into 80, 60, 50 or 40-pound bags, and the concrete calculator handles slab and footing volumes.
Maine frost depth FAQ
How deep is the frost line in Maine?
Maine has two code depths, and the county you build in decides which one an inspector measures: 48 inches in Southern & coastal, and 72 inches in Northern & western mountains. These are code values, not the average depth the ground actually froze last winter.
How deep do footings have to go in Maine?
Bearing sits below the frost depth, so dig to the code depth plus 6 inches: 48 inches of frost means a 54-inch dig, and 72 inches of frost means a 78-inch dig in Maine. The extra 6 inches is the bearing layer that keeps the footing from sitting on frost-susceptible soil, and it is what MUBEC (IRC) Table R301.2(1) expects to see on a permit drawing.
How do I know which Maine zone my county is in?
The citation in the table above names the authority that drew the lines — MUBEC (IRC) Table R301.2(1); Town Table R301.2(1). Your county or city publishes its own amendment to IRC Table R301.2(1) (or its own zone map), and that local document, not a state table, is what a permit reviewer checks. One call to the building department settles it before you rent an auger.
Plan a pour in Maine
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Last updated: 2026-11-02