Frost Line Depth in Gallatin County, MT: Montana Codes Range 36

No official local value

No official frost line depth is published for Gallatin County.

No verified code nearby; verified Montana codes range 36–42 in.

Source and how we checked

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

Climate: 180 nights a year at or below 32 °F (NOAA 1991–2020, Bozeman 6 W Exp Farm, 10.7 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

36–42 inrange of verified Montana codes
180nights a year at or below 32 °F
99%of nearby soil rated “moderate” for frost action (USDA)

Does Gallatin County have an official frost line depth?

No adopted frost line depth found for Gallatin County in its official documents (checked Oct 2026). No verified code lies near Gallatin County; the Montana codes we verified range from 36 to 42 in. Ask the building department for Gallatin County’s own number before you dig.

What frost line depth does Gallatin County 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 Gallatin County 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 Gallatin County?

Drawn with the deepest Montana official value (42 in). Confirm Gallatin County’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in Gallatin County: 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 Gallatin County 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 Gallatin County?

Average lows are at or below freezing from Nov to Apr. 180 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 14.5 °F.

NOAA 1991–2020 climate normals, Bozeman 6 W Exp Farm station, 10.7 mi away, elevation 4,775 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	15.4	17.3	24.6	31.1	39.3	45.2	51	49.5	42.4	32.7	22.4	14.5
High	34.3	36.6	46.6	55.3	64.5	72.4	82.6	82.4	72.1	57.6	42.5	33.5

Gallatin County has more freezing nights than 6 of the 7 other Montana places we track. The Montana median is 167. Coldest: Yellowstone County; mildest: Great Falls.

How likely is the soil in Gallatin County to heave?

Moderate 99%

USDA rates the sampled soil around Gallatin County as 1% low, 99% moderate for frost action (main soils: Typic Cryochrepts, Mollic Cryoboralfs, Bowery).

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

Gallatin County at a glance

Frost line depth: No official local value
Population (2023 est.): 126,409
Mean annual temperature: 44.4 °F
ZIP codes (10): 59086 · 59714 · 59715 · 59716 · 59718 · 59730 · 59741 · 59752 · 59758 · 59760