Accessory Structures in Hawaii County, HI (2026)
4 rules for unincorporated Hawaii County, Hawaii.
Verified from official government sources
ADU Rules
Hawai'i County allows one ohana dwelling (accessory dwelling unit) on RS, RA, FA and A zoned lots. The lot must be a legal lot of record, meet height, yard and parking rules, and have adequate sewage, water, fire and street access.
Ohana Dwellings (ADUs) in Hawai'i County
Some RestrictionsHCC 25-6-33(a); 25-6-35(a)
Regardless of the size of a building site, not more than one ohana dwelling unit shall be permitted on the same building site with the first single-family dwelling unit. The minimum building site area for a building site containing both the first dwelling and the ohana dwelling unit shall be ten thousand square feet.
ADU Rental Restrictions
Hawaii County caps transient accommodation rental use of an accessory dwelling unit at one per building site, and only if no other transient rental already operates there. The limit sits inside the same zoning article that sets ADU density, yard and parking standards, and it applies island-wide since Big Island has no separate city layer.
ADU Transient Rental Rules in Hawaii County
Significant RestrictionsHawaii County Code § 25-6-38
Section 25-6-38. Permitted uses. No more than one accessory dwelling unit shall be permitted for use as a transient accommodation rental, provided there are no other transient accommodation rentals on the building site.
Shed & Carport Rules
A tool shed, storage shed, greenhouse, or similar detached accessory building on Hawai'i Island skips the county building permit only if it sits on residential or agricultural land, stays under 200 square feet (residential) or 1,000 square feet (agricultural), stands no more than 15 feet tall, and sits at least 10 feet from the property line. Every accessory structure is separately capped at 20 feet countywide under the zoning code.
Accessory Building and Shed Rules on Big Island
Some RestrictionsHawai'i County Code § 25-4-23; § 5-3-22(a)(1)(D)
Section 25-4-23. Accessory structure height limitations. An accessory structure shall not exceed twenty feet in height, unless otherwise specified in this chapter. ... Section 5-3-22. Building work; exempt. (a) A permit shall not be required for any of the following building work, provided no electrical work or plumbing work is proposed: ... (D) Detached one-story accessory structures of U occu...
Tiny Homes
Hawaii County rewrote Appendix Q of the International Residential Code and adopted it into HCC § 5B-3-3, giving tiny houses their own construction rules. A tiny house is capped at 500 square feet of floor area excluding lofts, may hold only one loft, and if it has a loft it can only be used as a detached single-family dwelling, not a duplicate unit or rental annex.
Tiny House Rules in Hawaii County
Some RestrictionsHawaii County Code § 5B-3-3 (Appendix Q, Tiny Houses)
AQ101.1 Scope. This appendix shall be applicable to tiny houses used as single dwelling units and tiny houses that contain a loft. Tiny houses shall comply with the International Residential Code except as otherwise stated in this appendix. AQ101.1.1 Limitations. Tiny houses shall not contain more than one loft, or loft space. Tiny houses that contain a loft may not be used for any purpose othe...
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