Frost Line Depth in Post Falls, Idaho
- Post Falls’s adopted code
- Checked Oct 2026
- Sources
Verified
24in
61 cm · 2 ft
Set in the building code Post Falls has adopted.
Source and how we checked
Document: postfallspolice.gov
Climate: 120 nights a year at or below 32 °F (NOAA 1991–2020, Coeur D'Alene, 7.5 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in Post Falls?
Post Falls' building authority sets the frost line depth at 24 in (61 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 Post Falls?
Idaho leaves the frost line depth to each city or county, and Post Falls fills it in when it adopts the residential code. The value above comes from Post Falls’s own document on postfallspolice.gov. See how Idaho sets frost line depth.
How deep do footings, decks and water lines need to be in Post Falls?
House or garage footing in Post Falls: dig at least 24 in (61 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| Project | Depth | Rule |
|---|---|---|
| House or garage footing | 24 in | Below the frost line and at least 12 in deep (IRC R403.1.4) |
| Deck footing (attached) | 24 in | Below the frost line and at least 12 in deep (IRC R507.3) |
| Water service line | 30 in | 6 in below the frost line and at least 12 in deep (IRC P2603.5) |
| Fence post bottom | 24 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 Post Falls?
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Average lows are at or below freezing from Nov to Mar. 120 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 26.2 °F.
NOAA 1991–2020 climate normals, Coeur D'Alene station, 7.5 mi away, elevation 2,133 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 26.2 | 26.5 | 30.7 | 36.7 | 44.3 | 50.9 | 57.3 | 56 | 48.3 | 38.7 | 31.6 | 26.3 |
| High | 36.2 | 40.7 | 48.4 | 56.2 | 65.8 | 72.1 | 82.8 | 83 | 73.7 | 58.4 | 44.2 | 36.1 |
Post Falls has fewer freezing nights than 9 of the 13 other Idaho places we track. The Idaho median is 132. Coldest: Madison County; mildest: Canyon County.
How likely is the soil in Post Falls to heave?
USDA rates the sampled soil around Post Falls as 5% low, 95% moderate for frost action (main soils: Garrison, Skalan, Avonville).
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 Post Falls?
Post Falls at a glance
- Frost line depth
- 24 in
- County
- Kootenai County
- Population (2023 est.)
- 44,798
- Mean annual temperature
- 48.8 °F
- ZIP codes (1)
- 83854