Frost Line Depth in Sioux City, IA: Iowa Codes Require 42 in

No official local value

No official frost line depth is published for Sioux City.

No verified code nearby; every verified Iowa code we read uses 42 in.

Source and how we checked

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

Climate: 160 nights a year at or below 32 °F (NOAA 1991–2020, Sioux City Ang, 6.9 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

42 inused by every verified Iowa code
160nights a year at or below 32 °F
92%of nearby soil rated “high” for frost action (USDA)

Does Sioux City have an official frost line depth?

No adopted frost line depth found for Sioux City in its official documents (checked Oct 2026). No verified code lies near Sioux City; every Iowa code we verified uses 42 in. Ask the building department for Sioux City’s own number before you dig.

What frost line depth does Sioux City use for footings under Table R301.2(1)?

Call 811 (Iowa One Call) at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Sioux City 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 Sioux City?

Drawn with the deepest Iowa official value (42 in). Confirm Sioux City’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in Sioux City: 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 Sioux City 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 Sioux City?

Average lows are at or below freezing from Nov to Mar. 160 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 8.7 °F.

NOAA 1991–2020 climate normals, Sioux City Ang station, 6.9 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	8.7	12.5	23.9	34.8	47.3	57.9	63.3	60.9	50.9	37.3	24.3	13.7
High	29.7	34.6	47.4	60.7	71.6	82.1	85.7	83	77.3	63.8	47.3	33.9

Sioux City has more freezing nights than 26 of the 28 other Iowa places we track. The Iowa median is 144. Coldest: Cerro Gordo County; mildest: Davenport.

How likely is the soil in Sioux City to heave?

High 92%

USDA rates the sampled soil around Sioux City as 8% moderate, 92% high for frost action (main soils: Ida, Albaton, Rawles).

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

Sioux City at a glance

Frost line depth: No official local value
County: Woodbury County
Population (2023 est.): 85,727
Mean annual temperature: 48 °F
ZIP codes (9): 51054 · 51101 · 51103 · 51104 · 51105 · 51106 · 51108 · 51109 · 51111