Frost Line Depth in Kirkland, Washington
- Kirkland’s adopted code
- Checked Oct 2026
- Sources
Verified
18in
46 cm · 1 ft 6 in
Set in the building code Kirkland has adopted.
Source and how we checked
Document: permits.kirklandwa.gov
Climate: 25 nights a year at or below 32 °F (NOAA 1991–2020, Seattle Sand Pt Wsfo, 2.5 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in Kirkland?
Kirkland's building authority sets the frost line depth at 18 in (46 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 Kirkland?
Washington leaves the frost line depth to each city or county, and Kirkland fills it in when it adopts the residential code. The value above comes from Kirkland’s own document on permits.kirklandwa.gov. King County, which covers the unincorporated land around Kirkland, uses 12 in Below 1,000 ft, Deeper Above, so check which one issues your permit. See how Washington sets frost line depth.
How deep do footings, decks and water lines need to be in Kirkland?
House or garage footing in Kirkland: dig at least 18 in (46 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| Project | Depth | Rule |
|---|---|---|
| House or garage footing | 18 in | Below the frost line and at least 12 in deep (IRC R403.1.4) |
| Deck footing (attached) | 18 in | Below the frost line and at least 12 in deep (IRC R507.3) |
| Water service line | 24 in | 6 in below the frost line and at least 12 in deep (IRC P2603.5) |
| Fence post bottom | 18 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 Kirkland?
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Kirkland never averages a low below freezing. 25 nights a year reach 32 °F or colder; Feb is coldest, with an average low of 37 °F.
NOAA 1991–2020 climate normals, Seattle Sand Pt Wsfo station, 2.5 mi away, elevation 60 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 37.2 | 37 | 39.2 | 42.8 | 48.3 | 52.7 | 56.5 | 57.1 | 53.2 | 46.7 | 40.9 | 37 |
| High | 47.4 | 49.8 | 53.9 | 58.8 | 65.3 | 70.2 | 76.5 | 77 | 71.3 | 60.5 | 51.9 | 46.5 |
Kirkland has fewer freezing nights than 43 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 Kirkland use?
5 official codes near Kirkland are verified; each links to its document.
| Place | Verified frost line | Distance |
|---|---|---|
| Redmond | 12 in | 4 mi away |
| Lynnwood | 18 in | 10 mi away |
| Everett | 18 in | 19 mi away |
| Lake Stevens | 12 in | 22 mi away |
| King County | 12 in | 22 mi away |
How likely is the soil in Kirkland to heave?
USDA rates the sampled soil around Kirkland as 100% none for frost action (main soils: Alderwood, Kitsap, Arents).
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 Kirkland?
Kirkland at a glance
- Frost line depth
- 18 in
- County
- King County
- Population (2023 est.)
- 91,194
- Mean annual temperature
- 53.2 °F
- ZIP codes (4)
- 98033 · 98034 · 98039 · 98072