Frost Line Depth in San Francisco, California
- 4 verified codes nearby
- Checked Oct 2026
No official local value
Frost rarely reaches the ground in San Francisco.
Nearby official codes require 5–30 in (4 verified codes).
Footings still go at least 12 in (30 cm) below undisturbed ground (IRC R403.1.4).
Source and how we checked
We searched this place’s own code and website and found no published frost line depth.
Climate: 1 night a year at or below 32 °F (NOAA 1991–2020, San Francisco Oceanside, 28.8 mi).
Checked Oct 2026. Report a correction
Does San Francisco have an official frost line depth?
No adopted frost line depth found for San Francisco in its official documents (checked Oct 2026). The nearest official values, from codes we verified, are 5 to 30 in. Use the deepest of them until the building department confirms San Francisco’s own number.
What frost line depth does San Francisco use for footings under Table R301.2(1)? Is it 5 in, like Palo Alto?
How deep do footings, decks and water lines need to be in San Francisco?
Drawn with the deepest nearby official value (30 in). Confirm San Francisco’s own depth before you dig.
House or garage footing in San Francisco: dig at least 30 in (76 cm). Below the frost line and at least 12 in deep (IRC R403.1.4).
| Project | Depth | Rule |
|---|---|---|
| House or garage footing | 30 in | Below the frost line and at least 12 in deep (IRC R403.1.4) |
| Deck footing (attached) | 30 in | Below the frost line and at least 12 in deep (IRC R507.3) |
| Water service line | 36 in | 6 in below the frost line and at least 12 in deep (IRC P2603.5) |
| Fence post bottom | 30 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 Francisco?
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
San Francisco never averages a low below freezing. 1 night a year reach 32 °F or colder; Jan is coldest, with an average low of 45.7 °F.
NOAA 1991–2020 climate normals, San Francisco Oceanside station, 28.8 mi away, elevation 8 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 45.7 | 46.6 | 47.9 | 49.1 | 51 | 52.7 | 54.3 | 55.4 | 55.3 | 53.2 | 49.5 | 45.8 |
| High | 59 | 60.4 | 60.8 | 60.4 | 59.8 | 60.9 | 61.8 | 63.7 | 65 | 66.4 | 63.5 | 59.1 |
San Francisco has fewer freezing nights than 135 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 Francisco use?
4 official codes near San Francisco are verified; each links to its document.
San Francisco at a glance
- Frost line depth
- No official local value
- County
- San Francisco County
- Population (2023 est.)
- 808,988
- Mean annual temperature
- 56.1 °F
- ZIP codes (30)
- 94102 · 94103 · 94104 · 94105 · 94107 · 94108 · 94109 · 94110 · 94111 · 94112 · 94114 · 94115 · 94116 · 94117 · 94118 · 94121 · 94122 · 94123 · 94124 · 94127 · 94129 · 94130 · 94131 · 94132 · 94133 · 94134 · 94158 · 94188 · 94501 · 94920