Buying Land in Hawaii County (the Big Island): Zoning and Lava Zone Basics

A-1, A-20, and A-40: the county's own tiers inside the state's Agricultural District

The Hawaii state hub explains that the statewide Agricultural District leaves minimum lot size and dwelling rules to each county. Hawaii County's own zoning code answers that with three agricultural tiers: A-1, with a one-acre minimum lot size and a single-family dwelling allowed as long as the property is used primarily for agriculture; A-20, with a 20-acre minimum and a density cap of one dwelling per 20 acres; and A-40, with a 40-acre minimum and one dwelling per 40 acres. Which tier applies to a given parcel is a county zoning-map question, not something you can infer from the "agricultural" label on a listing -- the difference between A-1 and A-40 land is the difference between a buildable one-acre lot and a 40-acre parcel that supports exactly one house.

Because the dwelling allowance is conditioned on the property being used "primarily" for agriculture, the county can and does ask for evidence of an actual farm operation -- not just a fence and a few fruit trees -- before signing off on a farm dwelling permit, particularly on A-20 and A-40 parcels where the agricultural use is the entire justification for the zoning. Confirm the specific documentation the Planning Department wants for your parcel's tier before assuming the dwelling allowance is automatic.

Lava flow hazard zones: a real, county-specific issue for insurance and financing, not just geology

The US Geological Survey maps the entire island into nine lava flow hazard zones, numbered 1 (most hazardous, based on frequency and coverage of past flows) through 9 (least hazardous) -- a system that applies only to Hawaii County, since it's tied to this island's active volcanoes (Kilauea, Mauna Loa, Hualalai, Mauna Kea, and Kohala). Zone 1 and Zone 2 land is concentrated on the lower flanks of Kilauea and Mauna Loa -- much of Puna and parts of South Kona and Ka'u -- and every specific parcel's zone can be looked up from its Tax Map Key.

This isn't just a disclosure footnote. Under Hawaii's real property disclosure law (HRS Chapter 508D), a seller must disclose known material facts tied to a parcel's TMK-mapped hazard designation, and lava zone status counts. Separately, HRS 431:10E-142 -- a statute specific to Hawaii County -- addresses insurance for lava zone properties directly, because most standard homeowner's carriers won't write new policies in Zones 1 and 2, leaving the state-created Hawaii Property Insurance Association (HPIA) as the practical last-resort market. Conventional secondary-market financing is also harder to find on Zone 1/2 land. None of this makes Zone 1 or 2 land unbuildable -- plenty of people live there -- but it changes the financing and insurance plan, and it's worth confirming directly with a lender and an HPIA-eligible insurer rather than assuming standard terms will apply.

Off-grid homesteading in Puna is a genuine, long-established market here

Partly because of the lava-zone economics above, Hawaii County -- and Puna in particular -- has one of the country's most active markets for cheap, large-lot land aimed at buyers planning to go off-grid: catchment water systems instead of county water, solar or generator power instead of grid connection, and (until the statewide 2050 phase-out forces a change) a cesspool instead of a permitted septic system. Decades-old subdivisions like Hawaiian Paradise Park -- one of the largest subdivisions by lot count in the US -- and Ainaloa were platted long before most lots had road paving, water lines, or reliable utility service, and many still don't. That's the tradeoff behind Puna's famously low per-acre prices: real acreage, genuinely inexpensive, but often without the infrastructure a mainland buyer would assume comes standard.

Two offices for everything: Hilo (East Hawaii) and Kona (West Hawaii)

Hawaii County's Planning Department and its Public Works Building Division both split their operations geographically, with a separate office in Hilo serving East Hawaii and one in Kailua-Kona serving West Hawaii -- which office to call depends on where the parcel sits, not which office is more convenient. Both handle zoning verification, subdivision review, SMA determinations, and permit issuance for their respective sides of the island.