Peoria County, IL Frost Line Depth: 42 in

Verified

42in

107 cm · 3 ft 6 in

Set in the building code Peoria County has adopted.

Source and how we checked

Document: peoriacounty.gov

Climate: 118 nights a year at or below 32 °F (NOAA 1991–2020, Peoria Gtr Peoria Airport, 9.3 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

1 of 2nearby verified codes use the same depth
118nights a year at or below 32 °F
90%of nearby soil rated “high” for frost action (USDA)

How deep is the frost line in Peoria County?

Peoria County's building authority sets the frost line depth 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 Peoria County?

Illinois leaves the frost line depth to each city or county, and Peoria County fills it in when it adopts the residential code. The value above comes from Peoria County’s own document on peoriacounty.gov. See how Illinois sets frost line depth.

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

House or garage footing Deck footing Water service line Fence post

House or garage footing in Peoria 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 Peoria 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 Peoria County?

Average lows are at or below freezing from Dec to Mar. 118 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 17.6 °F.

NOAA 1991–2020 climate normals, Peoria Greater Peoria Airport station, 9.3 mi away, elevation 650 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	17.6	21.4	31.6	42.1	52.8	62.4	66.3	64.4	56.3	44.4	33	23.2
High	33.6	38.7	51.2	63.7	74.2	83.2	86.3	84.6	78.4	65.4	50.8	38.5

Peoria County has fewer freezing nights than 50 of the 71 other Illinois places we track. The Illinois median is 127. Coldest: Hoffman Estates; mildest: Madison County.

What frost line depth do towns near Peoria County use?

2 official codes near Peoria County are verified; each links to its document.

Official frost line depths near Peoria County
Place	Verified frost line	Distance
Bloomington	40 in	47 mi away
LaSalle County	42 in	60 mi away

How likely is the soil in Peoria County to heave?

High 90%

USDA rates the sampled soil around Peoria County as 10% moderate, 90% high for frost action (main soils: Rozetta, Dorchester, Marseilles).

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 Peoria County?

Call 811 (JULIE) at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Peoria 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.

Peoria County at a glance

Frost line depth: 42 in
Population (2023 est.): 177,513
Mean annual temperature: 52.7 °F
ZIP codes (28): 61451 · 61489 · 61517 · 61523 · 61525 · 61526 · 61528 · 61529 · 61531 · 61533 · 61536 · 61539 · 61547 · 61552 · 61559 · 61562 · 61565 · 61569 · 61602 · 61603 · 61604 · 61605 · 61606 · 61607 · 61614 · 61615 · 61616 · 61625