Frost Line Depth in Douglas County, OR: 18 in (Oregon rule)

State-set value

18in

46 cm · 1 ft 6 in

18 in (Oregon rule)

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

Source and how we checked

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

Document: codes.iccsafe.org

Climate: 38 nights a year at or below 32 °F (NOAA 1991–2020, Winchester, 10 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

38nights a year at or below 32 °F
100%of nearby soil rated “low” for frost action (USDA)

How deep is the frost line in Douglas County?

Oregon sets the frost footing depth for Douglas County at 18 in (46 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 Douglas County?

Oregon writes this depth into its statewide residential code, so Douglas County’s building department enforces the state’s number rather than setting its own. See how Oregon sets frost line depth.

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

House or garage footing Deck footing Water service line Fence post

House or garage footing in Douglas County: dig at least 18 in (46 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Minimum depths in Douglas County with a 18 in frost line
Project	Depth	Rule
House or garage footing	18 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	18 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	24 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	18 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 Douglas County?

Douglas County never averages a low below freezing. 38 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 34.7 °F.

NOAA 1991–2020 climate normals, Winchester station, 10 mi away, elevation 460 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	34.7	35.2	36.8	39.8	45.2	50.2	54.9	53.9	48.8	42.6	38.4	34.8
High	50	54.2	59.2	64	71.4	77.2	85.9	86.4	80.5	68	55.5	48.9

Douglas County has fewer freezing nights than 17 of the 22 other Oregon places we track. The Oregon median is 54. Coldest: Deschutes County; mildest: Lincoln County.

How likely is the soil in Douglas County to heave?

Low 100%

USDA rates the sampled soil around Douglas County as 0% none, 100% low for frost action (main soils: Dickerson, Sutherlin, Redbell).

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 Douglas County?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Douglas County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 18 in unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

Douglas County at a glance

Frost line depth: 18 in (Oregon rule)
Population (2023 est.): 112,435
Mean annual temperature: 54.9 °F
ZIP codes (30): 97410 · 97416 · 97417 · 97424 · 97429 · 97432 · 97435 · 97436 · 97441 · 97442 · 97443 · 97447 · 97457 · 97459 · 97462 · 97467 · 97469 · 97470 · 97471 · 97473 · 97479 · 97481 · 97484 · 97486 · 97493 · 97494 · 97495 · 97496 · 97499 · 97731