Frost depth in North Dakota
North Dakota has two code depths: 48 inches in 60 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" / 66". 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 |
|---|---|---|---|
| Fargo & southern tier | 48" | 54" | Fargo Municipal Code (IRC amendments) |
| Northern tier (Minot, Grand Forks) | 60" | 66" | Local 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 North Dakota's number looks the way it does
North Dakota is second only to Alaska in frost severity. Fargo and the southern tier dig 48 inches; the northern tier — Minot, Grand Forks — goes to 60, and anyone who has left a shallow fence post out through a prairie winter has watched the ground push it back up.
From frost depth to dig depth in North Dakota
Footings bear on undisturbed soil below the frost line, so the hole goes 6 inches deeper than the code number. In North Dakota that means:
| Code frost depth | Dig depth | Shortest Sonotube |
|---|---|---|
| 48" | 54" | 6 ft tube |
| 60" | 66" | 6 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 48–60 inches below grade.
How much concrete a footing takes in North Dakota
Bags of 80-lb mix per footing, for a solid pier with no post in the hole, at North Dakota's code depth:
| Frost depth | 10" hole | 12" hole | 16" hole | 20" hole |
|---|---|---|---|---|
| 48" (54" dig) | 5 bags | 6 bags | 11 bags | 17 bags |
| 60" (66" dig) | 5 bags | 8 bags | 13 bags | 20 bags |
The bags calculator converts any total into 80, 60, 50 or 40-pound bags, and the concrete calculator handles slab and footing volumes.
North Dakota frost depth FAQ
How deep is the frost line in North Dakota?
North Dakota has two code depths, and the county you build in decides which one an inspector measures: 48 inches in Fargo & southern tier, and 60 inches in Northern tier (Minot, Grand Forks). These are code values, not the average depth the ground actually froze last winter.
How deep do footings have to go in North Dakota?
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 60 inches of frost means a 66-inch dig in North Dakota. The extra 6 inches is the bearing layer that keeps the footing from sitting on frost-susceptible soil, and it is what Fargo Municipal Code (IRC amendments) expects to see on a permit drawing.
How do I know which North Dakota zone my county is in?
The citation in the table above names the authority that drew the lines — Fargo Municipal Code (IRC amendments); Local 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 North Dakota
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Last updated: 2026-11-02