Frost Line Depth in Redwood City, California
- 5 verified codes nearby
- Checked Oct 2026
No official local value
No official frost line depth is published for Redwood City.
Nearby official codes require 5–30 in (5 verified codes).
Source and how we checked
We searched this place’s own code and website and found no published frost line depth.
Climate: 6 nights a year at or below 32 °F (NOAA 1991–2020, Redwood City, 3 mi).
Checked Oct 2026. Report a correction
Does Redwood City have an official frost line depth?
No adopted frost line depth found for Redwood City 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 Redwood City’s own number.
What frost line depth does Redwood City 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 Redwood City?
Drawn with the deepest nearby official value (30 in). Confirm Redwood City’s own depth before you dig.
House or garage footing in Redwood City: 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 Redwood City?
- J
- F
- M
- A
- M
- J
- J
- A
- S
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- N
- D
Redwood City never averages a low below freezing. 6 nights a year reach 32 °F or colder; Dec is coldest, with an average low of 40.2 °F.
NOAA 1991–2020 climate normals, Redwood City station, 3 mi away, elevation 31 ft.
Monthly temperatures as a table
| °F | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | 40.5 | 42.5 | 44.6 | 46.5 | 50.4 | 53.6 | 56.6 | 56.5 | 54.3 | 49.8 | 43.9 | 40.2 |
| High | 58.9 | 61.9 | 65.3 | 68.5 | 72.9 | 78.8 | 81 | 80.8 | 79.3 | 74.6 | 64.7 | 58.6 |
Redwood City has more freezing nights than 117 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 Redwood City use?
5 official codes near Redwood City are verified; each links to its document.
| Place | Verified frost line | Distance |
|---|---|---|
| Palo Alto | 5 in | 9 mi away |
| Campbell | 12 in | 22 mi away |
| Dublin | 12 in | 22 mi away |
| Santa Cruz | 12 in | 39 mi away |
| Brentwood | 30 in | 40 mi away |
How likely is the soil in Redwood City to heave?
USDA rates the sampled soil around Redwood City as 100% none for frost action (main soils: Urban land, Orthents, Reyes).
USDA NRCS soil survey, 9 sample points within 2 mi. Higher frost action means more risk of heave; see frost heave.
Redwood City at a glance
- Frost line depth
- No official local value
- County
- San Mateo County
- Population (2023 est.)
- 80,996
- Mean annual temperature
- 59.4 °F
- ZIP codes (6)
- 94002 · 94061 · 94062 · 94063 · 94065 · 94070