Frost Line Depth in Sullivan County, NH: Nearby Codes Require 48 in

No official local value

No official frost line depth is published for Sullivan County.

Nearby official codes require 48 in (2 verified codes).

Source and how we checked

We searched this place’s own code and website and found no published frost line depth.

Climate: 186 nights a year at or below 32 °F (NOAA 1991–2020, Newport, 2.3 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

48 in2 verified codes within 56 mi
186nights a year at or below 32 °F
81%of nearby soil rated “moderate” for frost action (USDA)

Does Sullivan County have an official frost line depth?

No adopted frost line depth found for Sullivan County in its official documents (checked Oct 2026). The nearest official values, from codes we verified, are 48 in. Use the deepest of them until the building department confirms Sullivan County’s own number.

What frost line depth does Sullivan County use for footings under Table R301.2(1)? Is it 48 in, like Concord?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Sullivan County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 48 in (the deepest nearby value) unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

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

Drawn with the deepest nearby official value (48 in). Confirm Sullivan County’s own depth before you dig.

House or garage footing Deck footing Water service line Fence post

House or garage footing in Sullivan County: dig at least 48 in (122 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).

Using the nearby official value of 48 in until Sullivan County confirms its own
Project	Depth	Rule
House or garage footing	48 in	Below the frost line and at least 12 in deep (IRC R403.1.4)
Deck footing (attached)	48 in	Below the frost line and at least 12 in deep (IRC R507.3)
Water service line	54 in	6 in below the frost line and at least 12 in deep (IRC P2603.5)
Fence post bottom	48 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 Sullivan County?

Average lows are at or below freezing from Nov to Apr. 186 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 9.1 °F.

NOAA 1991–2020 climate normals, Newport station, 2.3 mi away, elevation 770 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	9.1	10	18.8	30.5	41.8	51.5	56.4	54.3	46.6	35.5	26.7	17
High	29.3	32.4	40.6	53.6	66.4	74.9	80.1	78.6	71	58	45.5	34.8

Sullivan County has more freezing nights than 5 of the 5 other New Hampshire places we track. The New Hampshire median is 171. Coldest: Sullivan County; mildest: Nashua.

What frost line depth do towns near Sullivan County use?

2 official codes near Sullivan County are verified; each links to its document.

Official frost line depths near Sullivan County
Place	Verified frost line	Distance
Concord	48 in	34 mi away
Nashua	48 in	56 mi away

How likely is the soil in Sullivan County to heave?

Moderate 81%High 13%

USDA rates the sampled soil around Sullivan County as 6% low, 81% moderate, 13% high for frost action (main soils: Monadnock, Peru, Sunapee).

USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.

Sullivan County at a glance

Frost line depth: No official local value
Population (2023 est.): 43,969
Mean annual temperature: 44.3 °F
ZIP codes (19): 03244 · 03257 · 03280 · 03284 · 03601 · 03602 · 03603 · 03605 · 03607 · 03743 · 03745 · 03748 · 03751 · 03752 · 03753 · 03770 · 03773 · 03781 · 03782