Frost Line Depth in Eugene, OR: 12 in (Oregon rule)

State-set value

12in

30 cm · 1 ft

12 in (Oregon rule)

Set by the state: Oregon Residential Specialty Code Table R301.2(1), Lane County.

Source and how we checked

Eugene does not publish its own value; the state rule applies.

Document: codes.iccsafe.org

Climate: 52 nights a year at or below 32 °F (NOAA 1991–2020, Eugene Mahlon Sweet Airport, 7 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

2 of 2nearby verified codes use the same depth
52nights a year at or below 32 °F
85%of nearby soil rated “low” for frost action (USDA)

How deep is the frost line in Eugene?

Oregon sets the frost footing depth for Eugene at 12 in (30 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 Eugene?

Oregon writes this depth into its statewide residential code, so Eugene’s building department enforces the state’s number rather than setting its own. Lane County uses the same 12 in, so the depth does not change at the city limits. See how Oregon sets frost line depth.

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

House or garage footing Deck footing Water service line Fence post

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

Minimum depths in Eugene with a 12 in frost line
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 Eugene?

Eugene never averages a low below freezing. 52 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 34.3 °F.

NOAA 1991–2020 climate normals, Eugene Mahlon Sweet Airport station, 7 mi away, elevation 353 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	34.7	35	37.2	40	44	47.6	51.7	51.5	47.8	41.8	37.7	34.3
High	48.1	51.5	56.6	61.3	68.1	74.2	84	84.3	78	64.9	53.2	46.8

Eugene has fewer freezing nights than 13 of the 22 other Oregon places we track. The Oregon median is 54. Coldest: Deschutes County; mildest: Lincoln County.

What frost line depth do towns near Eugene use?

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

Official frost line depths near Eugene
Place	Verified frost line	Distance
Corvallis	12 in	36 mi away
Marion County	12 in	64 mi away

How likely is the soil in Eugene to heave?

None 15%Low 85%

USDA rates the sampled soil around Eugene as 15% none, 85% low for frost action (main soils: Malabon, Ritner, Salem).

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 Eugene?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Eugene building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 12 in unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

Eugene at a glance

Frost line depth: 12 in (Oregon rule)
County: Lane County
Population (2023 est.): 177,899
Mean annual temperature: 53.1 °F
ZIP codes (6): 97401 · 97402 · 97403 · 97404 · 97405 · 97408