Frost Line Depth in Anchorage Municipality, Alaska
- Anchorage Municipality’s adopted code
- Checked Oct 2026
- Sources
Verified
42in
107 cm · 3 ft 6 in
42 in (60 in for Cold Foundations)
Set in the building code Anchorage Municipality has adopted.
Source and how we checked
Document: library.municode.com
Climate: 204 nights a year at or below 32 °F (NOAA 1991–2020, Eagle Rvr Nature Ctr, 4.2 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in Anchorage Municipality?
Anchorage Municipality's building authority sets the frost line depth at 42 in (107 cm) for a heated foundation and 60 in (152 cm) for an unheated (cold) one. Footings, piers and other permanent supports must reach at least this depth (IRC R403.1.4.1).
Who sets the frost line depth in Anchorage Municipality?
Alaska leaves the frost line depth to each city or county, and Anchorage Municipality fills it in when it adopts the residential code. The value above comes from Anchorage Municipality’s own document on library.municode.com. See how Alaska sets frost line depth.
How deep do footings, decks and water lines need to be in Anchorage Municipality?
House or garage footing in Anchorage Municipality: dig at least 42 in (107 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| Project | Depth | Rule |
|---|---|---|
| House or garage footing | 42 in | Below the frost line and at least 12 in deep (IRC R403.1.4) |
| Deck footing (attached) | 42 in | Below the frost line and at least 12 in deep (IRC R507.3) |
| Water service line | 48 in | 6 in below the frost line and at least 12 in deep (IRC P2603.5) |
| Fence post bottom | 42 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 Anchorage Municipality?
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Average lows are at or below freezing from Oct to Apr. 204 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 6.4 °F.
NOAA 1991–2020 climate normals, Eagle Rvr Nature Ctr station, 4.2 mi away, elevation 520 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 6.4 | 11.6 | 14.7 | 26.5 | 35.7 | 43.7 | 47.9 | 44.9 | 37.2 | 25.7 | 12.9 | 8.9 |
| High | 20.9 | 28 | 35.3 | 47.1 | 58 | 65.4 | 67.4 | 64.5 | 56 | 42.1 | 26.4 | 23.3 |
How likely is the soil in Anchorage Municipality to heave?
USDA rates the sampled soil around Anchorage Municipality as 0% low, 34% moderate, 66% high for frost action (main soils: E23-boreal subalpine scrub/meadow mosaic-silty till slopes, E23-boreal alpine scrub-gravelly colluvial slopes, E23-boreal forest-silty till slopes).
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 Anchorage Municipality?
Anchorage Municipality at a glance
- Frost line depth
- 42 in (60 in for Cold Foundations)
- Population (2023 est.)
- 286,075
- Mean annual temperature
- 35.5 °F
- ZIP codes (18)
- 99501 · 99502 · 99503 · 99504 · 99505 · 99506 · 99507 · 99508 · 99513 · 99515 · 99516 · 99517 · 99518 · 99530 · 99540 · 99567 · 99577 · 99587