ADU rules in Waipahu, HI — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Waipahu homeowners in this dense former plantation town may build one accessory dwelling unit per zoning lot in eligible residential districts, supporting multi-generational Filipino households under the Honolulu LUO.
ROH Sec. 21-5.720 permits one ADU per zoning lot in Country, R-3.5, R-5, R-7.5, R-10, and R-20 districts, covering most Waipahu residential blocks. ADUs must meet minimum lot-size, parking, occupancy, and setback standards. Short-term rentals under 30 days are prohibited. The ordinance has after-the-fact permit provisions for structures built without permits before September 14, 2015. Ordinance 25-2 (2025) amended several provisions. ADUs are especially relevant to Waipahu's many multi-generational Filipino households seeking to keep extended family close while adding legal rental capacity.
Building an ADU without a permit, short-term renting an ADU, or exceeding one ADU per lot may result in fines and abatement orders from DPP.
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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 Waipahu's adu rules rules stack up against other locations.
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