Frost Line Depth in Shiawassee County, Michigan

Michigan state rule
Checked Oct 2026
Sources

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

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

Document: codes.iccsafe.org

Climate: 149 nights a year at or below 32 °F (NOAA 1991–2020, Owosso Wwtp, 4.8 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

1 of 1nearby verified codes use the same depth
149nights a year at or below 32 °F
57%of nearby soil rated “high” for frost action (USDA)

How deep is the frost line in Shiawassee County?

Michigan sets the frost footing depth for Shiawassee 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 Shiawassee County?

Michigan writes this depth into its statewide residential code, so Shiawassee 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 Shiawassee County?

House or garage footing Deck footing Water service line Fence post

House or garage footing in Shiawassee 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 Shiawassee 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 Shiawassee County?

Average lows are at or below freezing from Nov to Mar. 149 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 15.7 °F.

NOAA 1991–2020 climate normals, Owosso Wwtp station, 4.8 mi away, elevation 730 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	15.7	16.3	23.8	34.5	46.2	56	59.7	58.5	51	40	30.7	22.5
High	30.3	33.1	43.3	56.5	68.7	78.1	81.9	80	73.5	60.6	47	35.5

Shiawassee County has more freezing nights than 49 of the 62 other Michigan places we track. The Michigan median is 143. Coldest: Marquette County; mildest: Allegan County.

What frost line depth do towns near Shiawassee County use?

One official code near Shiawassee County is verified.

Official frost line depths near Shiawassee County
Place	Verified frost line	Distance
Montcalm County	42 in	56 mi away

How likely is the soil in Shiawassee County to heave?

Moderate 43%High 57%

USDA rates the sampled soil around Shiawassee County as 43% moderate, 57% high for frost action (main soils: Wawasee, Conover, Matherton).

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 Shiawassee 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 Shiawassee 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.

Shiawassee County at a glance

Frost line depth: 42 in (Michigan rule)
Population (2023 est.): 68,025
Mean annual temperature: 47.6 °F
ZIP codes (19): 48414 · 48418 · 48429 · 48433 · 48436 · 48449 · 48460 · 48476 · 48616 · 48649 · 48817 · 48831 · 48840 · 48841 · 48848 · 48857 · 48866 · 48867 · 48872