Sussex County, DE Frost Line Depth: 24 in

Verified

24in

61 cm · 2 ft

Set in the building code Sussex County has adopted.

Source and how we checked

Document: sussexcountyde.gov

Climate: 83 nights a year at or below 32 °F (NOAA 1991–2020, Georgetown Sussex Co Airport, 1.6 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

0 of 1nearby verified codes use the same depth
83nights a year at or below 32 °F
67%of nearby soil rated “low” for frost action (USDA)

How deep is the frost line in Sussex County?

"{confirmed quote}". Footings, piers and other permanent supports must reach at least this depth (IRC R403.1.4.1).

Who sets the frost line depth in Sussex County?

Delaware has no statewide residential code, so Sussex County adopts its own and fills in the frost line depth. The value above comes from Sussex County’s own document on sussexcountyde.gov. See how Delaware sets frost line depth.

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

House or garage footing Deck footing Water service line Fence post

House or garage footing in Sussex County: dig at least 24 in (61 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Minimum depths in Sussex County with a 24 in frost line
Project	Depth	Rule
House or garage footing	24 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	24 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	30 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	24 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 Sussex County?

Average lows are at or below freezing from Jan to Feb. 83 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 28.6 °F.

NOAA 1991–2020 climate normals, Georgetown Sussex Co Airport station, 1.6 mi away, elevation 51 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	28.6	30	36.3	45.3	54.5	64	69.5	67.7	61.2	49.4	39.6	32.7
High	45.2	47.8	55.2	66.3	74.5	83.1	87.7	85.7	79.5	69.3	58.7	49.9

What frost line depth do towns near Sussex County use?

One official code near Sussex County is verified.

Official frost line depths near Sussex County
Place	Verified frost line	Distance
Wilmington	32 in	74 mi away

How likely is the soil in Sussex County to heave?

Low 67%Moderate 31%

USDA rates the sampled soil around Sussex County as 67% low, 31% moderate, 2% high for frost action (main soils: Hammonton, Pepperbox, Rosedale).

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 Sussex County?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Sussex County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 24 in unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

Sussex County at a glance

Frost line depth: 24 in
Population (2023 est.): 263,509
Mean annual temperature: 57.6 °F
ZIP codes (24): 19930 · 19931 · 19933 · 19939 · 19940 · 19941 · 19944 · 19945 · 19947 · 19950 · 19951 · 19952 · 19956 · 19958 · 19960 · 19963 · 19966 · 19967 · 19968 · 19970 · 19971 · 19973 · 19975 · 21874