Marysville, WA Frost Line Depth: 18 in

Verified

18in

46 cm · 1 ft 6 in

Set in the building code Marysville has adopted.

Source and how we checked

Document: docs.marysvillewa.gov

Climate: 51 nights a year at or below 32 °F (NOAA 1991–2020, Everett, 7.5 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

3 of 4nearby verified codes use the same depth
51nights a year at or below 32 °F
77%of nearby soil rated “none” for frost action (USDA)

How deep is the frost line in Marysville?

Marysville's building authority sets the frost line depth 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 Marysville?

Washington leaves the frost line depth to each city or county, and Marysville fills it in when it adopts the residential code. The value above comes from Marysville’s own document on docs.marysvillewa.gov. Snohomish County uses the same 18 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 Marysville?

House or garage footing Deck footing Water service line Fence post

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

Minimum depths in Marysville 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 Marysville?

Marysville never averages a low below freezing. 51 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 34.1 °F.

NOAA 1991–2020 climate normals, Everett station, 7.5 mi away, elevation 60 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	34.6	34.5	37.2	41.4	47	51.8	55.3	55.2	49.6	43.3	37.6	34.1
High	47.9	50.4	54.5	59.6	65.8	69.8	74.8	75.7	70.4	60.7	52.4	46.7

Marysville has fewer freezing nights than 26 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 Marysville use?

4 official codes near Marysville are verified; each links to its document.

Official frost line depths near Marysville
Place	Verified frost line	Distance
Lake Stevens	12 in	6 mi away
Everett	18 in	8 mi away
Snohomish County	18 in	18 mi away
Lynnwood	18 in	19 mi away

How likely is the soil in Marysville to heave?

None 77%Low 23%

USDA rates the sampled soil around Marysville as 77% none, 23% low for frost action (main soils: Tokul, Ragnar, Custer).

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 Marysville?

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

Marysville at a glance

Frost line depth: 18 in
County: Snohomish County
Population (2023 est.): 72,916
Mean annual temperature: 52.1 °F
ZIP codes (5): 98201 · 98223 · 98270 · 98271 · 98292