Frostline.info

Frost line depth in San Bernardino County, California

Frost reaches about 4 inches in typical soil across San Bernardino County, from 0″ in the mildest ZIP code to 8″ in the coldest. Codes in this climate commonly set footing depth at 12 inches (code minimum).

Shallow frost
Estimated frost depth
4″
typical silt/loam soil
Typical code footing depth
12″ minimum
rule of thumb for this climate
Design freezing index
14
°F-days, 100-year winter
ZIP codes covered
76
#25 of 58 counties in CA (1 = deepest)
4″ 0″12″24″36″ ground frozen
Est. frost (typical soil) Typical code footing depth Clay–sand range

Frost depth by soil type

Soil typeEst. frost depth
Sand / gravel (drains well)5″
Silt / loam (typical yard soil)4″
Clay (holds water)3″

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 Bernardino County building or permitting office in California and call 811 before digging.

Frost depth by ZIP code in San Bernardino County

ZIPCityEst. frostCode range
91701Rancho Cucamonga0″12″ minimum
91708Chino0″12″ minimum
91709Chino Hills0″12″ minimum
91710Chino0″12″ minimum
91730Rancho Cucamonga0″12″ minimum
91737Rancho Cucamonga0″12″ minimum
91739Rancho Cucamonga0″12″ minimum
91758Ontario0″12″ minimum
91761Ontario0″12″ minimum
91762Ontario0″12″ minimum
91763Montclair0″12″ minimum
91764Ontario0″12″ minimum
91784Upland0″12″ minimum
91786Upland0″12″ minimum
92242Earp0″12″ minimum
92252Joshua Tree2″12″ minimum
92256Morongo Valley0″12″ minimum
92277Twentynine Palms2″12″ minimum
92280Vidal0″12″ minimum
92284Yucca Valley1″12″ minimum
92285Landers2″12″ minimum
92301Adelanto6″12–18″
92305Angelus Oaks6″12–18″
92307Apple Valley6″12–18″
92308Apple Valley7″12–18″
92309Baker5″12–18″
92310Fort Irwin4″12″ minimum
92311Barstow5″12–18″
92313Grand Terrace0″12″ minimum
92314Big Bear City7″12–18″
92315Big Bear Lake7″12–18″
92316Bloomington0″12″ minimum
92318Bryn Mawr0″12″ minimum
92323Cima6″12–18″
92324Colton0″12″ minimum
92327Daggett3″12″ minimum
92332Essex1″12″ minimum
92335Fontana0″12″ minimum
92336Fontana0″12″ minimum
92337Fontana0″12″ minimum
92338Ludlow3″12″ minimum
92339Forest Falls5″12–18″
92342Helendale5″12–18″
92344Hesperia7″12–18″
92345Hesperia7″12–18″
92346Highland4″12″ minimum
92347Hinkley5″12–18″
92354Loma Linda0″12″ minimum
92356Lucerne Valley8″12–18″
92358Lytle Creek0″12″ minimum
92359Mentone3″12″ minimum
92363Needles0″12″ minimum
92364Nipton7″12–18″
92365Newberry Springs3″12″ minimum
92366Mountain Pass6″12–18″
92368Oro Grande6″12–18″
92371Phelan7″12–18″
92372Pinon Hills4″12″ minimum
92373Redlands0″12″ minimum
92374Redlands1″12″ minimum
92376Rialto0″12″ minimum
92377Rialto0″12″ minimum
92392Victorville6″12–18″
92394Victorville6″12–18″
92395Victorville6″12–18″
92397Wrightwood3″12″ minimum
92399Yucaipa0″12″ minimum
92401San Bernardino2″12″ minimum
92403San Bernardino2″12″ minimum
92404San Bernardino1″12″ minimum
92405San Bernardino2″12″ minimum
92407San Bernardino6″12–18″
92408San Bernardino0″12″ minimum
92410San Bernardino0″12″ minimum
92411San Bernardino0″12″ minimum
93562Trona4″12″ minimum

What this means for your project in San Bernardino 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 — 14 °F-days here — to size perimeter insulation, letting footings sit shallower than the frost line.

Weather stations used

NOAA weather stationDistance100-yr AFI
Lake Arrowhead, CA11 mi124
Victorville Pump Plant, CA20 mi36
San Bernardino Co Hosp, CA20 mi0
Redlands, CA23 mi0

Nearby counties

Common questions

What is the frost line depth in San Bernardino County?

About 4 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 8 inches.

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

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

Does frost depth vary within San Bernardino County?

Yes. Estimates differ by 8 inches between the coldest and mildest ZIP codes, mostly from latitude and elevation. Check your own ZIP below.