Frost Line Depth in San Jose, California
- San Jose’s adopted code
- Checked Oct 2026
- Sources
Verified
5in
13 cm · 5 in
Set in the building code San Jose 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: 2 nights a year at or below 32 °F (NOAA 1991–2020, San Jose, 6.1 mi).
Checked Oct 2026. Report a correction
How deep is the frost line in San Jose?
San Jose's building authority sets the frost line depth at 5 in (13 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 San Jose?
California leaves the frost line depth to each city or county, and San Jose fills it in when it adopts the residential code. The value above comes from San Jose’s own document on up.codes. See how California sets frost line depth.
How deep do footings, decks and water lines need to be in San Jose?
House or garage footing in San Jose: 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 San Jose?
- J
- F
- M
- A
- M
- J
- J
- A
- S
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- N
- D
San Jose never averages a low below freezing. 2 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 42.8 °F.
NOAA 1991–2020 climate normals, San Jose station, 6.1 mi away, elevation 67 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 43.3 | 45.4 | 47.6 | 49.8 | 53.3 | 57 | 59.1 | 59.8 | 58.2 | 53.8 | 47.2 | 42.8 |
| High | 59 | 62.8 | 66.4 | 70 | 74.9 | 80.1 | 82.2 | 82.7 | 81.4 | 74.6 | 65 | 58.8 |
San Jose has fewer freezing nights than 114 of the 208 other California places we track. The California median is 3. Coldest: El Dorado County; mildest: San Diego.
What frost line depth do towns near San Jose use?
5 official codes near San Jose are verified; each links to its document.
| Place | Verified frost line | Distance |
|---|---|---|
| Campbell | 12 in | 8 mi away |
| Palo Alto | 5 in | 19 mi away |
| Santa Cruz | 12 in | 25 mi away |
| Watsonville | 12 in | 26 mi away |
| Dublin | 12 in | 29 mi away |
How likely is the soil in San Jose to heave?
USDA rates the sampled soil around San Jose as 100% none for frost action (main soils: Urban land, Montara, Elpaloalto).
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 San Jose?
San Jose at a glance
- Frost line depth
- 5 in
- County
- Santa Clara County
- Population (2023 est.)
- 969,655
- Mean annual temperature
- 61.4 °F
- ZIP codes (39)
- 95002 · 95008 · 95013 · 95014 · 95032 · 95035 · 95037 · 95050 · 95051 · 95054 · 95070 · 95110 · 95111 · 95112 · 95113 · 95116 · 95117 · 95118 · 95119 · 95120 · 95121 · 95122 · 95123 · 95124 · 95125 · 95126 · 95127 · 95128 · 95129 · 95130 · 95131 · 95132 · 95133 · 95134 · 95135 · 95136 · 95138 · 95139 · 95148