Frost Line Depth in Maricopa County, Arizona

Maricopa County’s adopted code
Checked Oct 2026
Sources

Verified

0in

No frost depth required

Set in the building code Maricopa County has adopted.

Footings still go at least 12 in (30 cm) below undisturbed ground (IRC R403.1.4).

Source and how we checked

Document: maricopa.gov

Climate: 7 nights a year at or below 32 °F (NOAA 1991–2020, Litchfield Park, 13.2 mi).

Checked Oct 2026. Report a correction

Footings Deck Water line Fence post

1 of 1nearby verified codes use the same depth
7nights a year at or below 32 °F
100%of nearby soil rated “none” for frost action (USDA)

How deep is the frost line in Maricopa County?

Maricopa County's building authority sets the frost line depth at 0 in (0 cm). Footings, piers and other permanent supports still go at least 12 in below undisturbed ground (IRC R403.1.4).

Who sets the frost line depth in Maricopa County?

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

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

House or garage footing Deck footing Water service line Fence post

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

Minimum depths in Maricopa County with a 0 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	12 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 Maricopa County?

Maricopa County never averages a low below freezing. 7 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 42 °F.

NOAA 1991–2020 climate normals, Litchfield Park station, 13.2 mi away, elevation 1,040 ft.

Monthly temperatures as a table

°F	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Low	42.9	45.9	51.2	57	65.3	73.7	81.2	80.6	73.8	60.9	49.3	42
High	66.1	70.2	77.7	85.5	94.3	104	106.5	104.7	99.3	88.1	74.6	64.5

Maricopa County has fewer freezing nights than 26 of the 35 other Arizona places we track. The Arizona median is 12. Coldest: Flagstaff; mildest: Yuma.

What frost line depth do towns near Maricopa County use?

One official code near Maricopa County is verified.

Official frost line depths near Maricopa County
Place	Verified frost line	Distance
Casa Grande	0 in	52 mi away

How likely is the soil in Maricopa County to heave?

None 100%

USDA rates the sampled soil around Maricopa County as 100% none for frost action (main soils: Antho, Gilman, Vint).

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 Maricopa County?

Call 811 at least a few working days before you dig, so buried lines are marked.
Confirm the frost line depth with the Maricopa County building department.
Ask whether your project needs a permit (decks, larger sheds and footings usually do).
Dig below 0 in unless the building department tells you otherwise.
Book the footing inspection before you pour concrete.

Maricopa County at a glance

Frost line depth: 0 in
Population (2023 est.): 4,585,871
Mean annual temperature: 73.3 °F
ZIP codes (140): 85003 · 85004 · 85006 · 85007 · 85008 · 85009 · 85012 · 85013 · 85014 · 85015 · 85016 · 85017 · 85018 · 85019 · 85020 · 85021 · 85022 · 85023 · 85024 · 85026 · 85027 · 85028 · 85029 · 85031 · 85032 · 85033 · 85034 · 85035 · 85037 · 85040 · 85041 · 85042 · 85043 · 85044 · 85045 · 85048 · 85050 · 85051 · 85053 · 85054 · 85083 · 85085 · 85086 · 85087 · 85120 · 85139 · 85142 · 85201 · 85202 · 85203 · 85204 · 85205 · 85206 · 85207 · 85208 · 85209 · 85210 · 85212 · 85213 · 85215 · 85224 · 85225 · 85226 · 85233 · 85234 · 85236 · 85248 · 85249 · 85250 · 85251 · 85253 · 85254 · 85255 · 85256 · 85257 · 85258 · 85259 · 85260 · 85262 · 85263 · 85264 · 85266 · 85268 · 85281 · 85282 · 85283 · 85284 · 85286 · 85295 · 85296 · 85297 · 85298 · 85301 · 85302 · 85303 · 85304 · 85305 · 85306 · 85307 · 85308 · 85309 · 85310 · 85320 · 85321 · 85322 · 85323 · 85326 · 85329 · 85331 · 85333 · 85335 · 85337 · 85338 · 85339 · 85340 · 85342 · 85343 · 85345 · 85351 · 85353 · 85354 · 85355 · 85361 · 85363 · 85373 · 85374 · 85375 · 85377 · 85378 · 85379 · 85381 · 85382 · 85383 · 85387 · 85388 · 85390 · 85392 · 85395 · 85396 · 85545