Frost Line Depth in Matanuska-Susitna Borough, AK: Alaska Codes Range 32

No official local value

No official frost line depth is published for Matanuska-Susitna Borough.

No verified code nearby; verified Alaska codes range 32–42 in.

Source and how we checked

We searched this place’s own code and website and found no published frost line depth.

Climate: 208 nights a year at or below 32 °F (NOAA 1991–2020, Talkeetna Airport, 19.4 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

32–42 inrange of verified Alaska codes
208nights a year at or below 32 °F
94%of nearby soil rated “high” for frost action (USDA)

Does Matanuska-Susitna Borough have an official frost line depth?

No adopted frost line depth found for Matanuska-Susitna Borough in its official documents (checked Oct 2026). No verified code lies near Matanuska-Susitna Borough; the Alaska codes we verified range from 32 to 42 in. Ask the building department for Matanuska-Susitna Borough’s own number before you dig.

What frost line depth does Matanuska-Susitna Borough use for footings under Table R301.2(1)?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Matanuska-Susitna Borough building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 42 in (the deepest verified state value) unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

How deep do footings, decks and water lines need to be in Matanuska-Susitna Borough?

Drawn with the deepest Alaska official value (42 in). Confirm Matanuska-Susitna Borough’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in Matanuska-Susitna Borough: dig at least 42 in (107 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Using the nearby official value of 42 in until Matanuska-Susitna Borough confirms its own
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 Matanuska-Susitna Borough?

Average lows are at or below freezing from Oct to Apr. 208 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 5.4 °F.

NOAA 1991–2020 climate normals, Talkeetna Airport station, 19.4 mi away, elevation 350 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	5.4	9.4	12.4	25.8	36.7	47	51.4	47.9	39	26.5	13.2	7.8
High	21.8	28.2	34.6	46.6	58.7	67.1	68.7	65.1	56	41.8	27.9	23.4

How likely is the soil in Matanuska-Susitna Borough to heave?

High 94%

USDA rates the sampled soil around Matanuska-Susitna Borough as 0% low, 6% moderate, 94% high for frost action (main soils: E23-boreal subalpine scrub/meadow mosaic-silty acid slopes, E23-boreal alpine scrub-silty acid hummocks, E23-boreal subalpine scrub-silty acid slopes).

USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.

Matanuska-Susitna Borough at a glance

Frost line depth: No official local value
Population (2023 est.): 115,239
Mean annual temperature: 35.9 °F
ZIP codes (12): 99588 · 99623 · 99645 · 99652 · 99654 · 99667 · 99674 · 99676 · 99683 · 99688 · 99694 · 99729