Frost line depth in Grand Forks County, North Dakota
Frost reaches about 61 inches in typical soil across Grand Forks County. Codes in this climate commonly set footing depth at 48 to 78 inches.
Severe frostFrost depth by soil type
| Soil type | Est. frost depth |
|---|---|
| Sand / gravel (drains well) | 77″ |
| Silt / loam (typical yard soil) | 61″ |
| Clay (holds water) | 53″ |
County average. Methodology.
Verify before you dig. These are climate-based estimates. The legally required frost depth is the figure your building department publishes in its IRC Table R301.2 (climatic and geographic design criteria). Call the Grand Forks County building or permitting office in North Dakota and call 811 before digging.
Frost depth by ZIP code in Grand Forks County
| ZIP | City | Est. frost | Code range |
|---|---|---|---|
| 58201 | Grand Forks | 61″ | 48–78″ |
| 58202 | Grand Forks | 61″ | 48–78″ |
| 58203 | Grand Forks | 61″ | 48–78″ |
| 58204 | Grand Forks AFB | 61″ | 48–78″ |
| 58205 | Grand Forks AFB | 61″ | 48–78″ |
| 58214 | Arvilla | 61″ | 48–78″ |
| 58228 | Emerado | 62″ | 48–78″ |
| 58235 | Gilby | 61″ | 48–78″ |
| 58244 | Inkster | 61″ | 48–78″ |
| 58251 | Larimore | 61″ | 48–78″ |
| 58256 | Manvel | 62″ | 48–78″ |
| 58258 | Mekinock | 61″ | 48–78″ |
| 58266 | Niagara | 63″ | 54–78″ |
| 58267 | Northwood | 61″ | 48–78″ |
| 58275 | Reynolds | 61″ | 48–78″ |
| 58278 | Thompson | 61″ | 48–78″ |
What this means for your project in Grand Forks County
Deck footings & piers
Footings must bear below the frost line and at least 12″ below undisturbed ground. For planning in this area, budget for holes around 78″ deep until your permit office confirms the exact figure.
Fence posts
Set posts at least one-third of their above-ground height. Where frost heave is a problem, carry concrete footings below the frost line (about 61″ here in typical soil) and bell or taper the bottom.
Water & irrigation lines
Bury supply lines below the frost depth. Your water utility or plumbing code sets the minimum cover; in a climate this cold, 4 feet or more is common for service lines.
Slabs & frost-protected foundations
Frost-protected shallow foundations (IRC R403.3) use the 100-year air freezing index — 3,883 °F-days here — to size perimeter insulation, letting footings sit shallower than the frost line.
Weather stations used
| NOAA weather station | Distance | 100-yr AFI |
|---|---|---|
| Grand Forks Airport, ND | 8 mi | 3,978 |
| Larimore, ND | 13 mi | 3,817 |
| Grand Forks University, ND | 13 mi | 3,836 |
| Mayville, ND | 30 mi | 3,691 |
Nearby counties
Common questions
What is the frost line depth in Grand Forks County?
About 61 inches in typical soil, based on NOAA's 100-year air freezing index. Across the county's ZIP codes the estimate runs from 61 to 63 inches.
How deep should footings be in Grand Forks County, North Dakota?
Codes in climates like this commonly require 48 to 78 inches. The Grand Forks County building department publishes the required frost depth in its adopted code (IRC Table R301.2).
Does frost depth vary within Grand Forks County?
Very little. Estimates across the county stay within 2 inches. Soil type matters more than location here.