Frost Line Depth in Phoenix, Arizona
- Phoenix’s adopted code
- Checked Oct 2026
- Sources
Verified
0in
No frost depth required
Set in the building code Phoenix has adopted.
Footings still go at least 12 in (30 cm) below undisturbed ground (IRC R403.1.4).
Source and how we checked
Document: up.codes
Climate: 3 nights a year at or below 32 °F (NOAA 1991–2020, Phoenix Deer Valley Municipal Airport, 8 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in Phoenix?
Phoenix'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 Phoenix?
Arizona has no statewide residential code, so Phoenix adopts its own and fills in the frost line depth. The value above comes from Phoenix’s own document on up.codes. Maricopa County uses the same 0 in, so the depth does not change at the city limits. See how Arizona sets frost line depth.
How deep do footings, decks and water lines need to be in Phoenix?
House or garage footing in Phoenix: dig at least 12 in (30 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| 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 Phoenix?
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Phoenix never averages a low below freezing. 3 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 42.7 °F.
NOAA 1991–2020 climate normals, Phoenix Deer Valley Municipal Airport station, 8 mi away, elevation 1,455 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 44.1 | 46.1 | 50.9 | 56.6 | 64.7 | 72.7 | 80.8 | 80.5 | 74.7 | 62.7 | 50.8 | 42.7 |
| High | 65.4 | 68.1 | 75 | 82.5 | 91.5 | 101.5 | 104 | 102.5 | 97.5 | 86.3 | 74 | 63.9 |
Phoenix has fewer freezing nights than 32 of the 35 other Arizona places we track. The Arizona median is 12. Coldest: Flagstaff; mildest: Yuma.
What frost line depth do towns near Phoenix use?
One official code near Phoenix is verified.
| Place | Verified frost line | Distance |
|---|---|---|
| Casa Grande | 0 in | 50 mi away |
How likely is the soil in Phoenix to heave?
USDA rates the sampled soil around Phoenix as 100% none for frost action (main soils: Gilman, Laveen, Ebon).
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 Phoenix?
Phoenix at a glance
- Frost line depth
- 0 in
- County
- Maricopa County
- Population (2023 est.)
- 1,650,070
- Mean annual temperature
- 72.5 °F
- ZIP codes (63)
- 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 · 85251 · 85253 · 85254 · 85255 · 85266 · 85281 · 85283 · 85301 · 85304 · 85305 · 85306 · 85307 · 85308 · 85310 · 85331 · 85339 · 85340 · 85353 · 85383