Frostline.info

Frost line depth in San Francisco County, California

Frost reaches about 0 inches in typical soil across San Francisco County. Codes in this climate commonly set footing depth at 12 inches (code minimum).

No meaningful frost
Estimated frost depth
0″
typical silt/loam soil
Typical code footing depth
12″ minimum
rule of thumb for this climate
Design freezing index
0
°F-days, 100-year winter
ZIP codes covered
30
#53 of 58 counties in CA (1 = deepest)
0″12″24″36″ ground
Est. frost (typical soil) Typical code footing depth Clay–sand range

Frost depth by soil type

Soil typeEst. frost depth
Sand / gravel (drains well)0″
Silt / loam (typical yard soil)0″
Clay (holds water)0″

County average. Methodology.

Verify before you dig. These are climate-based estimates. The legally required frost depth is the figure your building department publishes in its IRC Table R301.2 (climatic and geographic design criteria). Call the San Francisco County building or permitting office in California and call 811 before digging.

Frost depth by ZIP code in San Francisco County

ZIPCityEst. frostCode range
94102San Francisco0″12″ minimum
94103San Francisco0″12″ minimum
94104San Francisco0″12″ minimum
94105San Francisco0″12″ minimum
94107San Francisco0″12″ minimum
94108San Francisco0″12″ minimum
94109San Francisco0″12″ minimum
94110San Francisco0″12″ minimum
94111San Francisco0″12″ minimum
94112San Francisco0″12″ minimum
94114San Francisco0″12″ minimum
94115San Francisco0″12″ minimum
94116San Francisco0″12″ minimum
94117San Francisco0″12″ minimum
94118San Francisco0″12″ minimum
94121San Francisco0″12″ minimum
94122San Francisco0″12″ minimum
94123San Francisco0″12″ minimum
94124San Francisco0″12″ minimum
94127San Francisco0″12″ minimum
94129San Francisco0″12″ minimum
94130San Francisco0″12″ minimum
94131San Francisco0″12″ minimum
94132San Francisco0″12″ minimum
94133San Francisco0″12″ minimum
94134San Francisco0″12″ minimum
94141San Francisco0″12″ minimum
94143San Francisco0″12″ minimum
94158San Francisco0″12″ minimum
94188San Francisco0″12″ minimum

What this means for your project in San Francisco County

Deck footings & piers

Footings must bear below the frost line and at least 12″ below undisturbed ground. For planning in this area, budget for holes around 12″ deep until your permit office confirms the exact figure.

Fence posts

Set posts at least one-third of their above-ground height. Where frost heave is a problem, carry concrete footings below the frost line (about 12″ here in typical soil) and bell or taper the bottom.

Water & irrigation lines

Bury supply lines below the frost depth. Your water utility or plumbing code sets the minimum cover; freezing is rare, but exposed pipes still need insulation.

Slabs & frost-protected foundations

Frost-protected shallow foundations (IRC R403.3) use the 100-year air freezing index — 0 °F-days here — to size perimeter insulation, letting footings sit shallower than the frost line.

Weather stations used

NOAA weather stationDistance100-yr AFI
S F Federal Bldg., CA1 mi0
San Francisco, CA11 mi0
Berkeley, CA12 mi0
Richmond, CA12 mi0

Nearby counties

Common questions

What is the frost line depth in San Francisco County?

About 0 inches in typical soil, based on NOAA's 100-year air freezing index. Across the county's ZIP codes the estimate runs from 0 to 0 inches.

How deep should footings be in San Francisco County, California?

Codes in climates like this commonly require 12 inches (code minimum). The San Francisco County building department publishes the required frost depth in its adopted code (IRC Table R301.2).

Does frost depth vary within San Francisco County?

Very little. Estimates across the county stay within 1 inches. Soil type matters more than location here.