Frost Line Depth in Lamar County, MS: Set Locally (Gulfport: 12 in)

No official local value

No official frost line depth is published for Lamar County.

No verified code nearby. The only verified Mississippi code we read, Gulfport’s, 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: 32 nights a year at or below 32 °F (NOAA 1991–2020, Hattiesburg 5Sw, 10.6 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

12 inGulfport, the only verified Mississippi code
32nights a year at or below 32 °F
100%of nearby soil rated “none” for frost action (USDA)

Does Lamar County have an official frost line depth?

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

What frost line depth does Lamar 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 Lamar 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 Lamar County?

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

House or garage footing Deck footing Water service line Fence post

House or garage footing in Lamar 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 Lamar 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 Lamar County?

Lamar County never averages a low below freezing. 32 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 37.8 °F.

NOAA 1991–2020 climate normals, Hattiesburg 5sw station, 10.6 mi away, elevation 385 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	37.8	41.2	47.9	54.1	62.4	69.5	71.8	71.5	66.9	56	45.7	40.3
High	59.7	64	71.1	77.5	84.2	89.7	91.2	91.4	87.9	79.4	69.3	61.8

Lamar County has fewer freezing nights than 12 of the 17 other Mississippi places we track. The Mississippi median is 41. Coldest: Olive Branch; mildest: Biloxi.

How likely is the soil in Lamar County to heave?

None 100%

USDA rates the sampled soil around Lamar County as 100% none for frost action (main soils: McLaurin, Trebloc, Osier).

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

Lamar County at a glance

Frost line depth: No official local value
Population (2023 est.): 66,217
Mean annual temperature: 66.4 °F
ZIP codes (6): 39401 · 39402 · 39429 · 39455 · 39475 · 39482