Need an ADU design or build in Honolulu County, HI? Honolulu County has about 998,747 residents (2024 estimate) and 1 incorporated cities and towns. Describe your project once: licensed ADU builders who work in Honolulu County get back to you.
ADU permits in Honolulu County are issued by each city, or by the county in unincorporated areas.
Services available in Honolulu County
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Detached ADU
Design and construction of a detached backyard unit, site-built or prefab, with the permit and utilities.
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Garage or interior conversion
Conversion of a garage, basement or part of the house into a legal accessory dwelling unit.
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ADU plans and permit
Feasibility, plans and permit application for an ADU before choosing a builder.
Frequently asked questions in Honolulu County
Do licensed ADU builders cover the whole of Honolulu County?
Most pros work across the county and neighboring counties. Enter your ZIP code in the form and we match you with pros who serve your exact area.
ADU Builders in Hawaii: all counties
Source: U.S. Census Bureau, Population Estimates Program (Vintage 2024) and Gazetteer Files (public domain), imported on 10/31/2026. Figures describe the incorporated place or county as published; they are shown for information only.