Frostline.info

Frost line depth in Honolulu County, Hawaii

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

Source: NOAA 100-year air freezing index (1951–80 station records) · Last reviewed

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
37
#2 of 5 counties in HI (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 Honolulu County building or permitting office in Hawaii and call 811 before digging.

Frost depth by ZIP code in Honolulu County

ZIPCityEst. frostCode range
96701Aiea0″12″ minimum
96706Ewa Beach0″12″ minimum
96707Kapolei0″12″ minimum
96712Haleiwa0″12″ minimum
96717Hauula0″12″ minimum
96730Kaaawa0″12″ minimum
96731Kahuku0″12″ minimum
96734Kailua0″12″ minimum
96744Kaneohe0″12″ minimum
96762Laie0″12″ minimum
96782Pearl City0″12″ minimum
96786Wahiawa0″12″ minimum
96789Mililani0″12″ minimum
96791Waialua0″12″ minimum
96792Waianae0″12″ minimum
96795Waimanalo0″12″ minimum
96797Waipahu0″12″ minimum
96813Honolulu0″12″ minimum
96814Honolulu0″12″ minimum
96815Honolulu0″12″ minimum
96816Honolulu0″12″ minimum
96817Honolulu0″12″ minimum
96818Honolulu0″12″ minimum
96819Honolulu0″12″ minimum
96821Honolulu0″12″ minimum
96822Honolulu0″12″ minimum
96825Honolulu0″12″ minimum
96826Honolulu0″12″ minimum
96850Honolulu0″12″ minimum
96853Jbphh0″12″ minimum
96854Wheeler Army Airfield0″12″ minimum
96857Schofield Barracks0″12″ minimum
96858Fort Shafter0″12″ minimum
96859Tripler Army Medical Center0″12″ minimum
96860Jbphh0″12″ minimum
96861Camp H M Smith0″12″ minimum
96863Mcbh Kaneohe Bay0″12″ minimum

What this means for your project in Honolulu 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
Kaneohe Mauka 781, HI6 mi0
Opaeula 870, HI14 mi0
Waialua 847, HI18 mi0

Nearby counties

Common questions

What is the frost line depth in Honolulu 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 Honolulu County, Hawaii?

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

Does frost depth vary within Honolulu County?

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