Frost Line Depth in Bismarck, North Dakota
- Bismarck’s adopted code
- Checked Oct 2026
- Sources
Verified
48in
122 cm · 4 ft
Set in the building code Bismarck has adopted.
Source and how we checked
Document: bismarcknd.gov
Climate: 182 nights a year at or below 32 °F (NOAA 1991–2020, Bismarck 2.4 Nnw, 1.8 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in Bismarck?
Bismarck's building authority sets the frost line depth at 48 in (122 cm). Footings, piers and other permanent supports must reach at least this depth (IRC R403.1.4.1).
Who sets the frost line depth in Bismarck?
North Dakota leaves the frost line depth to each city or county, and Bismarck fills it in when it adopts the residential code. The value above comes from Bismarck’s own document on bismarcknd.gov. Burleigh County uses the same 48 in, so the depth does not change at the city limits. See how North Dakota sets frost line depth.
How deep do footings, decks and water lines need to be in Bismarck?
House or garage footing in Bismarck: dig at least 48 in (122 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| Project | Depth | Rule |
|---|---|---|
| House or garage footing | 48 in | Below the frost line and at least 12 in deep (IRC R403.1.4) |
| Deck footing (attached) | 48 in | Below the frost line and at least 12 in deep (IRC R507.3) |
| Water service line | 54 in | 6 in below the frost line and at least 12 in deep (IRC P2603.5) |
| Fence post bottom | 48 in | No code rule; common practice is below the frost line |
Work out posts, concrete and footing sizes with the fence post depth calculator or the deck footing calculator.
How cold does it get in Bismarck?
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Average lows are at or below freezing from Nov to Apr. 182 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 3.8 °F.
NOAA 1991–2020 climate normals, Bismarck 2.4 Nnw station, 1.8 mi away, elevation 1,831 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 3.8 | 6.7 | 17.8 | 29.4 | 42.5 | 52.5 | 58.3 | 55.6 | 46.1 | 33.5 | 19.8 | 9.5 |
| High | 22.1 | 27.1 | 39.7 | 53.8 | 66.4 | 75.6 | 81.5 | 80.1 | 71.3 | 55.6 | 39.6 | 26.9 |
What frost line depth do towns near Bismarck use?
One official code near Bismarck is verified.
| Place | Verified frost line | Distance |
|---|---|---|
| Burleigh County | 48 in | 18 mi away |
How likely is the soil in Bismarck to heave?
USDA rates the sampled soil around Bismarck as 5% low, 92% moderate, 3% high for frost action (main soils: Williams, Arnegard, Havrelon).
USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.
How do you confirm the frost line before you dig in Bismarck?
Bismarck at a glance
- Frost line depth
- 48 in
- County
- Burleigh County
- Population (2023 est.)
- 75,092
- Mean annual temperature
- 42.3 °F
- ZIP codes (4)
- 58501 · 58503 · 58504 · 58505