ADU rules in Honolulu, HI — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Honolulu allows one accessory dwelling unit on residential lots of 3,500 sq ft or more. Size is capped at 400–800 sq ft depending on lot size. Owner must live on the property and ADUs may only be rented long-term (six-month minimum).
ROH § 21-5.720 permits one ADU on lots zoned R-3.5, R-5, R-7.5, R-10, R-20, or Country District with a minimum lot area of 3,500 sq ft and adequate infrastructure. Maximum unit size is 400 sq ft for lots between 3,500 and 4,999 sq ft, and 800 sq ft for lots of 5,000 sq ft or more. The owner — or a family member related by blood, marriage, or adoption — must occupy either the main home or the ADU whenever the other unit is rented. The ADU may not be used as a short-term rental (bed and breakfast or transient vacation unit); all leases must be in writing for at least six months. One additional off-street parking space
Violation of the owner-occupancy covenant or the long-term rental requirement is enforceable by the Director of Planning and Permitting under ROH §§ 21-2.150 et seq., including fines and orders to cease unpermitted use.
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Side-by-side rule comparisons with other cities in Honolulu County.
See how other cities in Honolulu County handle adu rules.
See how Honolulu's adu rules rules stack up against other locations.
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