Frost Line Depth in Sanilac County, MI: 42 in (Michigan rule)

State-set value

42in

107 cm · 3 ft 6 in

42 in (Michigan rule)

Set by the state: Michigan Residential Code R403.1.4 (R 408.30522); the building official may modify.

Source and how we checked

Sanilac County does not publish its own value; the state rule applies.

Document: codes.iccsafe.org

Climate: 151 nights a year at or below 32 °F (NOAA 1991–2020, Sandusky, 9.1 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

151nights a year at or below 32 °F
61%of nearby soil rated “moderate” for frost action (USDA)

How deep is the frost line in Sanilac County?

Michigan sets the frost footing depth for Sanilac County at 42 in (107 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 Sanilac County?

Michigan writes this depth into its statewide residential code, so Sanilac County’s building department enforces the state’s number rather than setting its own. See how Michigan sets frost line depth.

How deep do footings, decks and water lines need to be in Sanilac County?

House or garage footing Deck footing Water service line Fence post

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

Minimum depths in Sanilac County with a 42 in frost line
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 Sanilac County?

Average lows are at or below freezing from Nov to Mar. 151 nights a year reach 32 °F or colder; Feb is coldest, with an average low of 14.2 °F.

NOAA 1991–2020 climate normals, Sandusky station, 9.1 mi away, elevation 774 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	14.7	14.2	23.6	33.2	45.4	56	60	58.2	50.8	40.1	30	22.4
High	28.4	30.9	40.7	53.8	66.5	76.5	80.1	78.2	72	58.6	45.2	34.2

Sanilac County has more freezing nights than 54 of the 62 other Michigan places we track. The Michigan median is 143. Coldest: Marquette County; mildest: Allegan County.

How likely is the soil in Sanilac County to heave?

Moderate 61%High 39%

USDA rates the sampled soil around Sanilac County as 61% moderate, 39% high for frost action (main soils: Guelph, McBride, Londo).

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 Sanilac County?

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

Sanilac County at a glance

Frost line depth: 42 in (Michigan rule)
Population (2023 est.): 40,368
Mean annual temperature: 46.4 °F
ZIP codes (23): 48032 · 48097 · 48401 · 48410 · 48416 · 48419 · 48422 · 48426 · 48427 · 48434 · 48441 · 48450 · 48453 · 48454 · 48456 · 48465 · 48466 · 48469 · 48470 · 48471 · 48472 · 48475 · 48726