Frost Line Depth in St. Croix County, Wisconsin

Wisconsin state rule
Checked Oct 2026
Sources

State-set value

48in

122 cm · 4 ft

48 in (Wisconsin rule)

Set by the state: Wisconsin Uniform Dwelling Code SPS 321.16 (minimum; deeper where frost goes deeper).

Source and how we checked

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

Document: docs.legis.wisconsin.gov

Climate: 169 nights a year at or below 32 °F (NOAA 1991–2020, Baldwin, 5.3 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

1 of 1nearby verified codes use the same depth
169nights a year at or below 32 °F
55%of nearby soil rated “moderate” for frost action (USDA)

How deep is the frost line in St. Croix County?

Wisconsin sets the frost footing depth for St. Croix County at 48 in (122 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 St. Croix County?

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

How deep do footings, decks and water lines need to be in St. Croix County?

House or garage footing Deck footing Water service line Fence post

House or garage footing in St. Croix County: dig at least 48 in (122 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Minimum depths in St. Croix County with a 48 in frost line
Project	Depth	Rule
House or garage footing	48 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	48 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	54 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	48 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 St. Croix County?

Average lows are at or below freezing from Nov to Mar. 169 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 1.8 °F.

NOAA 1991–2020 climate normals, Baldwin station, 5.3 mi away, elevation 1,100 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	1.8	4.9	19.2	32.5	44.8	55.7	59	56.7	48.5	35.8	23.4	10.1
High	20.3	25.9	37.4	53.9	65.6	75.9	79.3	77.4	71.1	56.2	40.1	26.7

St. Croix County has more freezing nights than 48 of the 52 other Wisconsin places we track. The Wisconsin median is 150. Coldest: Marinette County; mildest: Racine.

What frost line depth do towns near St. Croix County use?

One official code near St. Croix County is verified.

Official frost line depths near St. Croix County
Place	Verified frost line	Distance
Chippewa County	48 in	57 mi away

How likely is the soil in St. Croix County to heave?

Low 12%Moderate 55%High 34%

USDA rates the sampled soil around St. Croix County as 12% low, 55% moderate, 34% high for frost action (main soils: Jewett, Skyberg, Arland).

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 St. Croix County?

Call 811 (Diggers Hotline) at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the St. Croix County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 48 in unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

St. Croix County at a glance

Frost line depth: 48 in (Wisconsin rule)
Population (2023 est.): 96,763
Mean annual temperature: 42.6 °F
ZIP codes (18): 54002 · 54005 · 54007 · 54013 · 54015 · 54016 · 54017 · 54020 · 54022 · 54023 · 54025 · 54026 · 54027 · 54028 · 54082 · 54734 · 54749 · 54767