Redmond, WA Frost Line Depth: 12 in

Verified

12in

30 cm · 1 ft

Set in the building code Redmond has adopted.

Source and how we checked

Document: redmond.municipal.codes

Climate: 25 nights a year at or below 32 °F (NOAA 1991–2020, Seattle Sand Pt Wsfo, 6.5 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

2 of 5nearby verified codes use the same depth
25nights a year at or below 32 °F
100%of nearby soil rated “none” for frost action (USDA)

How deep is the frost line in Redmond?

Redmond'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 Redmond?

Washington leaves the frost line depth to each city or county, and Redmond fills it in when it adopts the residential code. The value above comes from Redmond’s own document on redmond.municipal.codes. King County uses the same 12 in, so the depth does not change at the city limits. See how Washington sets frost line depth.

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

House or garage footing Deck footing Water service line Fence post

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

Minimum depths in Redmond 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 Redmond?

Redmond never averages a low below freezing. 25 nights a year reach 32 °F or colder; Feb is coldest, with an average low of 37 °F.

NOAA 1991–2020 climate normals, Seattle Sand Pt Wsfo station, 6.5 mi away, elevation 60 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	37.2	37	39.2	42.8	48.3	52.7	56.5	57.1	53.2	46.7	40.9	37
High	47.4	49.8	53.9	58.8	65.3	70.2	76.5	77	71.3	60.5	51.9	46.5

Redmond has fewer freezing nights than 43 of the 47 other Washington places we track. The Washington median is 54. Coldest: Chelan County; mildest: Lakewood.

What frost line depth do towns near Redmond use?

5 official codes near Redmond are verified; each links to its document.

Official frost line depths near Redmond
Place	Verified frost line	Distance
Lynnwood	18 in	14 mi away
King County	12 in	18 mi away
Everett	18 in	20 mi away
Lake Stevens	12 in	23 mi away
Marysville	18 in	28 mi away

How likely is the soil in Redmond to heave?

None 100%

USDA rates the sampled soil around Redmond as 100% none for frost action (main soils: Alderwood, Puget, Kitsap).

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 Redmond?

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

Redmond at a glance

Frost line depth: 12 in
County: King County
Population (2023 est.): 80,280
Mean annual temperature: 53.2 °F
ZIP codes (4): 98007 · 98033 · 98052 · 98053