Frost Line Depth in St. Clair County, AL: Alabama Codes Require 12 in

No official local value

No official frost line depth is published for St. Clair County.

No verified code nearby; every verified Alabama code we read uses 12 in.

Source and how we checked

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

Climate: 65 nights a year at or below 32 °F (NOAA 1991–2020, Oneonta, 15.6 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

12 inused by every verified Alabama code
65nights a year at or below 32 °F
100%of nearby soil rated “none” for frost action (USDA)

Does St. Clair County have an official frost line depth?

No adopted frost line depth found for St. Clair County in its official documents (checked Oct 2026). No verified code lies near St. Clair County; every Alabama code we verified uses 12 in. Ask the building department for St. Clair County’s own number before you dig.

What frost line depth does St. Clair 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 St. Clair County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 12 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 St. Clair County?

Drawn with the deepest Alabama official value (12 in). Confirm St. Clair County’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in St. Clair County: dig at least 12 in (30 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Using the nearby official value of 12 in until St. Clair County confirms its own
Project	Depth	Rule
House or garage footing	12 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	12 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	18 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	12 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. Clair County?

St. Clair County never averages a low below freezing. 65 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 32.9 °F.

NOAA 1991–2020 climate normals, Oneonta station, 15.6 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	32.9	35.4	42.4	49.5	58.7	66.9	70.4	69.5	62.7	51.4	41.2	35.4
High	53.2	57.3	66	73.8	80.8	87.3	90.9	89.8	84.9	75	64.2	55.4

St. Clair County has more freezing nights than 32 of the 39 other Alabama places we track. The Alabama median is 52. Coldest: Tallapoosa County; mildest: Mobile.

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

None 100%

USDA rates the sampled soil around St. Clair County as 100% none for frost action (main soils: Nauvoo, Townley, Minvale).

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

St. Clair County at a glance

Frost line depth: No official local value
Population (2023 est.): 95,552
Mean annual temperature: 62.3 °F
ZIP codes (18): 35004 · 35052 · 35054 · 35094 · 35112 · 35120 · 35121 · 35125 · 35128 · 35131 · 35133 · 35135 · 35146 · 35173 · 35178 · 35953 · 35972 · 35987