Yakima County, WA Frost Line Depth: 12 in

Verified

12in

30 cm · 1 ft

Set in the building code Yakima County has adopted.

Source and how we checked

Document: yakimacounty.us

Climate: 109 nights a year at or below 32 °F (NOAA 1991–2020, Yakima #2, 12.1 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

109nights a year at or below 32 °F
75%of nearby soil rated “high” for frost action (USDA)

How deep is the frost line in Yakima County?

Yakima County's building authority sets the frost line depth 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 Yakima County?

Washington leaves the frost line depth to each city or county, and Yakima County fills it in when it adopts the residential code. The value above comes from Yakima County’s own document on yakimacounty.us. See how Washington sets frost line depth.

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

House or garage footing Deck footing Water service line Fence post

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

Minimum depths in Yakima County 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 Yakima County?

Average lows are at or below freezing from Nov to Feb. 109 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 25.7 °F.

NOAA 1991–2020 climate normals, Yakima #2 station, 12.1 mi away, elevation 1,142 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	26.8	30.4	34.2	40	47.9	53.8	59.7	58.7	51.4	40.2	32	25.7
High	39.6	47.9	57.3	65	73.5	79.6	88.3	87.9	79.4	64.4	48.6	37.8

Yakima County has more freezing nights than 35 of the 47 other Washington places we track. The Washington median is 54. Coldest: Chelan County; mildest: Lakewood.

How likely is the soil in Yakima County to heave?

Moderate 25%High 75%

USDA rates the sampled soil around Yakima County as 25% moderate, 75% high for frost action (main soils: Shano, Rock Creek, Warden).

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 Yakima County?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Yakima County 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.

Yakima County at a glance

Frost line depth: 12 in
Population (2023 est.): 256,643
Mean annual temperature: 52.9 °F
ZIP codes (22): 98901 · 98902 · 98903 · 98908 · 98921 · 98923 · 98930 · 98932 · 98933 · 98935 · 98936 · 98937 · 98938 · 98939 · 98942 · 98944 · 98947 · 98948 · 98951 · 98952 · 98953 · 99350