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

No official local value

No official frost line depth is published for Belknap 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: 150 nights a year at or below 32 °F (NOAA 1991–2020, Lakeport 2, 2.9 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

48 in2 verified codes within 53 mi
150nights a year at or below 32 °F
73%of nearby soil rated “moderate” for frost action (USDA)

Does Belknap County have an official frost line depth?

No adopted frost line depth found for Belknap 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 Belknap County’s own number.

What frost line depth does Belknap 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 Belknap 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 Belknap County?

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

House or garage footing Deck footing Water service line Fence post

House or garage footing in Belknap 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 Belknap 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 Belknap County?

Average lows are at or below freezing from Nov to Mar. 150 nights a year reach 32 °F or colder; Jan is coldest, with an average low of 11.7 °F.

NOAA 1991–2020 climate normals, Lakeport 2 station, 2.9 mi away, elevation 500 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	11.7	12.5	21.2	32.7	44.5	54.8	60.4	58.7	51.5	39.9	30	20.2
High	30.3	33.7	42.5	55.6	68	76.6	82.1	80.8	73.3	60.1	47.3	36.2

Belknap County has fewer freezing nights than 4 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 Belknap County use?

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

Official frost line depths near Belknap County
Place	Verified frost line	Distance
Concord	48 in	21 mi away
Nashua	48 in	53 mi away

How likely is the soil in Belknap County to heave?

Moderate 73%High 14%

USDA rates the sampled soil around Belknap County as 11% none, 2% low, 73% moderate, 14% high for frost action (main soils: Tunbridge, Lyman, Henniker).

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

Belknap County at a glance

Frost line depth: No official local value
Population (2023 est.): 65,027
Mean annual temperature: 46.9 °F
ZIP codes (15): 03218 · 03220 · 03225 · 03226 · 03237 · 03246 · 03249 · 03253 · 03254 · 03256 · 03269 · 03276 · 03809 · 03810 · 03837