Frost Line Depth in San Luis Obispo County, California
- California range from verified codes
- Checked Oct 2026
No official local value
Frost rarely reaches the ground in San Luis Obispo County.
No verified code nearby; verified California codes range 0–30 in.
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: 3 nights a year at or below 32 °F (NOAA 1991–2020, San Luis Obispo Poly, 13.3 mi).
Checked Oct 2026. Report a correction
Does San Luis Obispo County have an official frost line depth?
No adopted frost line depth found for San Luis Obispo County in its official documents (checked Oct 2026). No verified code lies near San Luis Obispo County; the California codes we verified range from 0 to 30 in. Ask the building department for San Luis Obispo County’s own number before you dig.
What frost line depth does San Luis Obispo County use for footings under Table R301.2(1)?
How deep do footings, decks and water lines need to be in San Luis Obispo County?
Drawn with the deepest California official value (30 in). Confirm San Luis Obispo County’s own depth before you dig.
House or garage footing in San Luis Obispo County: 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 Luis Obispo County?
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
San Luis Obispo County never averages a low below freezing. 3 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 43.7 °F.
NOAA 1991–2020 climate normals, San Luis Obispo Poly station, 13.3 mi away, elevation 308 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 44 | 44.4 | 46.1 | 46.8 | 49.3 | 51.8 | 54.2 | 54.8 | 53.8 | 51.5 | 47.4 | 43.7 |
| High | 64.9 | 65.2 | 67.3 | 69.3 | 71.9 | 75.7 | 78.3 | 79.7 | 80.1 | 77.8 | 70.8 | 64.4 |
San Luis Obispo County has fewer freezing nights than 99 of the 208 other California places we track. The California median is 3. Coldest: El Dorado County; mildest: San Diego.
How likely is the soil in San Luis Obispo County to heave?
USDA rates the sampled soil around San Luis Obispo County as 100% none for frost action (main soils: Cieneba, Rock outcrop, Shimmon).
USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.
San Luis Obispo County at a glance
- Frost line depth
- No official local value
- Population (2023 est.)
- 281,639
- Mean annual temperature
- 60.6 °F
- ZIP codes (30)
- 93252 · 93254 · 93401 · 93402 · 93405 · 93407 · 93408 · 93409 · 93410 · 93420 · 93422 · 93424 · 93426 · 93428 · 93430 · 93432 · 93433 · 93434 · 93442 · 93444 · 93445 · 93446 · 93449 · 93451 · 93452 · 93453 · 93454 · 93458 · 93461 · 93465