Accessory Structures in Hawaii (2026)
22 rules on the books across Hawaii, 5 cities and counties. Select a rule to read the full details.
Severity: Few Restrictions · Light Restrictions · Some Restrictions · Significant Restrictions · Heavy Restrictions
ADU Rules
Rules for building accessory dwelling units (granny flats, in-law suites) including size limits, parking requirements, and owner-occupancy rules.
Hawaii: statewide
StatewideSome RestrictionsAct 39 (2024), codified at HRS § 46-4.8, requires every county to amend its zoning to allow at least two accessory…
Read full rule →East Honolulu
Some RestrictionsEast Honolulu (City and County of Honolulu) permits one accessory dwelling unit on residential and country lots of…
Read full rule →Hawaii County
Some RestrictionsHawai'i County allows one ohana dwelling (accessory dwelling unit) on RS, RA, FA and A zoned lots. The lot must be a…
Read full rule →Honolulu County
Some RestrictionsOahu accessory dwelling units are capped at 500 square feet on zoning lots up to 4,999 square feet and 1,000 square…
Read full rule →Kauai County
Some RestrictionsOn Kaua'i (Kaua'i County), a residentially zoned lot with only one single-family home may add one more dwelling unit…
Read full rule →Maui County
Some RestrictionsMaui County caps an accessory dwelling at 720 to 1,200 square feet of gross covered floor area, scaled to lot size. A…
Read full rule →ADU Impact Fees
Impact fees, school fees, utility hookup charges, and waivers for ADUs. Many jurisdictions exempt ADUs under 750 sq ft from impact fees per state law.
Kauai County
Some RestrictionsOn Kaua'i (Kaua'i County), owners adding an Additional Rental Unit (ARU) can tap a County-funded subsidy to help pay…
Read full rule →Maui County
Some RestrictionsAn accessory dwelling on Maui pays only half the water system development fee that a standalone home owes. Maui County…
Read full rule →ADU Rental Restrictions
Whether an ADU can be rented short-term (Airbnb), 30-day minimums, separate rental licenses, and long-term lease requirements.
Maui County
Heavy RestrictionsMaui County flatly bars any accessory dwelling from operating as a bed and breakfast home, short-term rental home, or…
Read full rule →Hawaii County
Significant RestrictionsHawaii County caps transient accommodation rental use of an accessory dwelling unit at one per building site, and only…
Read full rule →Honolulu County
Significant RestrictionsOwners must record a covenant limiting an accessory dwelling unit to long-term residential occupancy: no bed and…
Read full rule →Kauai County
Few RestrictionsKaua'i County Code Section 22-28.2 blocks private covenants, deed restrictions and HOA bylaws from limiting or…
Read full rule →Shed & Carport Rules
When a storage shed or carport needs a permit, the square-footage exemption thresholds, and the setback and height limits that apply either way.
Honolulu County
Significant RestrictionsA one- or two-car carport or garage may encroach into a required front or side yard on Oahu only with a…
Read full rule →Hawaii County
Some RestrictionsA tool shed, storage shed, greenhouse, or similar detached accessory building on Hawai'i Island skips the county…
Read full rule →Kauai County
Some RestrictionsKaua'i County exempts small accessory buildings and garden sheds under seven feet tall and 400 square feet from…
Read full rule →Maui County
Light RestrictionsMaui County's building code exempts small detached accessory structures like sheds from needing a building permit, but…
Read full rule →East Honolulu
Few RestrictionsIn East Honolulu (City and County of Honolulu), a one-story detached storage shed accessory to a home is exempt from a…
Read full rule →Garage Conversions
Rules for converting a garage into living space, including whether you need to replace the lost parking and what building codes apply.
East Honolulu
Some RestrictionsIn East Honolulu (City and County of Honolulu), an existing legally established accessory structure such as a detached…
Read full rule →Honolulu County
Some RestrictionsROH § 21-2.140-1(n) lets an existing, legally built accessory structure on Oahu, like a detached garage put up before…
Read full rule →Tiny Homes
Zoning rules for tiny houses on wheels and foundations, including minimum square footage requirements and where they can be placed.
Hawaii: statewide
StatewideFew RestrictionsHawaii's Act 39 (2024), codified at HRS §46-4.8, orders every county to allow at least two accessory dwelling units, or…
Read full rule →Hawaii County
Some RestrictionsHawaii County rewrote Appendix Q of the International Residential Code and adopted it into HCC § 5B-3-3, giving tiny…
Read full rule →Kauai County
Light RestrictionsOn Kaua'i (Kaua'i County), Building Code Section 12-2.4 lets a homeowner build a Tiny House under the International…
Read full rule →