Frost Line Depth in Waukesha, WI: 48 in (Wisconsin rule)

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

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

Document: docs.legis.wisconsin.gov

Climate: 143 nights a year at or below 32 °F (NOAA 1991–2020, Waukesha Wwtp, 0.3 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

143nights a year at or below 32 °F
67%of nearby soil rated “moderate” for frost action (USDA)

How deep is the frost line in Waukesha?

Wisconsin sets the frost footing depth for Waukesha 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 Waukesha?

Wisconsin writes this depth into its statewide residential code, so Waukesha’s building department enforces the state’s number rather than setting its own. Waukesha County uses the same 48 in, so the depth does not change at the city limits. See how Wisconsin sets frost line depth.

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

House or garage footing Deck footing Water service line Fence post

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

Minimum depths in Waukesha 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 Waukesha?

Average lows are at or below freezing from Nov to Mar. 143 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 11.6 °F.

NOAA 1991–2020 climate normals, Waukesha Wwtp station, 0.3 mi away, elevation 789 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	11.6	14.6	24	34.8	45.8	55.6	60.3	58.9	51.1	39.8	28.3	18.1
High	27.7	31.5	43	55.3	67.3	77.4	81.4	79.8	72.9	60	45	33

Waukesha has fewer freezing nights than 34 of the 52 other Wisconsin places we track. The Wisconsin median is 150. Coldest: Marinette County; mildest: Racine.

How likely is the soil in Waukesha to heave?

Moderate 67%High 33%

USDA rates the sampled soil around Waukesha as 67% moderate, 33% high for frost action (main soils: Hochheim, Houghton, Loamy land).

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 Waukesha?

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 Waukesha 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.

Waukesha at a glance

Frost line depth: 48 in (Wisconsin rule)
County: Waukesha County
Population (2023 est.): 70,446
Mean annual temperature: 46.6 °F
ZIP codes (4): 53072 · 53186 · 53188 · 53189