Frost Line Depth in Franklin County, Washington
- Franklin County’s adopted code
- Checked Oct 2026
- Sources
Verified
24in
61 cm · 2 ft
Set in the building code Franklin County has adopted.
Source and how we checked
Document: franklincountywa.gov
Climate: 115 nights a year at or below 32 °F (NOAA 1991–2020, Connell 1 W, 8.8 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in Franklin County?
Franklin County's 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 Franklin County?
Washington leaves the frost line depth to each city or county, and Franklin County fills it in when it adopts the residential code. The value above comes from Franklin County’s own document on franklincountywa.gov. See how Washington sets frost line depth.
How deep do footings, decks and water lines need to be in Franklin County?
House or garage footing in Franklin County: 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 Franklin County?
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Average lows are at or below freezing from Nov to Feb. 115 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 26.6 °F.
NOAA 1991–2020 climate normals, Connell 1 W station, 8.8 mi away, elevation 1,020 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 26.6 | 28.9 | 32.4 | 37.3 | 44.3 | 50.1 | 55.2 | 54.8 | 47.3 | 37.6 | 31.3 | 27.2 |
| High | 39.2 | 46.1 | 55.8 | 64.7 | 73.8 | 80.3 | 89.6 | 88.1 | 79.2 | 63.9 | 47.6 | 38.5 |
Franklin County has more freezing nights than 39 of the 47 other Washington places we track. The Washington median is 54. Coldest: Chelan County; mildest: Lakewood.
What frost line depth do towns near Franklin County use?
One official code near Franklin County is verified.
| Place | Verified frost line | Distance |
|---|---|---|
| Pasco | 24 in | 21 mi away |
How likely is the soil in Franklin County to heave?
USDA rates the sampled soil around Franklin County as 100% high for frost action (main soils: Shano, Ritzville, Warden).
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 Franklin County?
Franklin County at a glance
- Frost line depth
- 24 in
- Population (2023 est.)
- 99,034
- Mean annual temperature
- 51.7 °F
- ZIP codes (7)
- 99301 · 99326 · 99330 · 99335 · 99343 · 99344 · 99371