Frost Line Depth in Jefferson County, MO: Missouri Codes Range 30

No official local value

No official frost line depth is published for Jefferson County.

No verified code nearby; verified Missouri codes range 30–36 in.

Source and how we checked

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

Climate: 105 nights a year at or below 32 °F (NOAA 1991–2020, Festus, 8.1 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

30–36 inrange of verified Missouri codes
105nights a year at or below 32 °F
77%of nearby soil rated “moderate” for frost action (USDA)

Does Jefferson County have an official frost line depth?

No adopted frost line depth found for Jefferson County in its official documents (checked Oct 2026). No verified code lies near Jefferson County; the Missouri codes we verified range from 30 to 36 in. Ask the building department for Jefferson County’s own number before you dig.

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

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Jefferson County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 36 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 Jefferson County?

Drawn with the deepest Missouri official value (36 in). Confirm Jefferson County’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in Jefferson County: dig at least 36 in (91 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Using the nearby official value of 36 in until Jefferson County confirms its own
Project	Depth	Rule
House or garage footing	36 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	36 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	42 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	36 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 Jefferson County?

Average lows are at or below freezing from Dec to Feb. 105 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 22.3 °F.

NOAA 1991–2020 climate normals, Festus station, 8.1 mi away, elevation 600 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	22.3	25.3	33.6	43.8	53.8	62.6	67.2	65.4	57.1	45.5	35.1	26.5
High	41	46.3	56.3	67.8	76.2	84.6	88.4	87.2	80.6	69.6	56	45.1

Jefferson County has fewer freezing nights than 5 of the 11 other Missouri places we track. The Missouri median is 105. Coldest: Buchanan County; mildest: Camden County.

How likely is the soil in Jefferson County to heave?

Moderate 77%High 23%

USDA rates the sampled soil around Jefferson County as 77% moderate, 23% high for frost action (main soils: Sonsac, Useful, Freeburg).

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

Jefferson County at a glance

Frost line depth: No official local value
Population (2023 est.): 231,230
Mean annual temperature: 55.7 °F
ZIP codes (25): 63010 · 63012 · 63015 · 63016 · 63019 · 63020 · 63023 · 63025 · 63026 · 63028 · 63030 · 63041 · 63047 · 63048 · 63049 · 63050 · 63051 · 63052 · 63053 · 63069 · 63070 · 63072 · 63087 · 63627 · 63628