Jack Tyrrell specializes in Kakaako, Honolulu, Hawaii luxury condo projects.

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Accessory Dwelling Units in Honolulu: What you need to know

Photo of converted garage by Martin John Brown,  accessorydwellings.org

Photo of converted garage by Martin John Brown, accessorydwellings.org

On September 14, 2015, Mayor Kirk Caldwell signed Bill 20, allowing accessory dwelling units, into law. This law will make it easier for you as a homeowner and investor to convert a part of your property into rental units or to build additional dwellings on your property.

According to the City and County of Honolulu's Department of Planning and Permitting, the "purpose of this Ordinance is to allow ADUs as a permitted use in Residential and Country zoning districts and to encourage and accommodate the construction of ADUs, which will increase the number of affordable rental units and help alleviate the housing shortage in the City." 

What kinds of opportunities do ADUs present to you as a homeowner and investor? Such units may provide you extra rental income. They also constitute as an asset-building strategy for you, and may improve the value of your property. Furthermore, according to the U.S. Department of Housing and Urban Development, "ADUs are smaller in size, do not require the extra expense of purchasing land, can be developed by converting existing structures, and do not require additional infrastructure."

Here are some quick answers to some of your questions, taken from the City website:

  • Where can I build an ADU? An ADU can be built on any lot zoned Residential (R-3.5, R-5, R-7.5, R-10, and R-20) or Country District with a lot area of 3,500 square feet (SF) or more provided that there is adequate infrastructure and subject to meeting all other Land Use Ordinance provisions for the zoning lot and there are no restrictive covenants. 
  • How big can an ADU be? An ADU can be a maximum of 400 SF for lots ranging between 3,500 SF and 4,999 SF and 800 SF for lots greater than 5,000 SF.
  • In addition to the principal dwelling unit, how many ADUs can I build on a single lot? Only one additional dwelling unit is permitted. ADUs are not permitted on lots that already have more than one dwelling unit, including but not necessarily limited to, more than one single-family dwelling, a two-family dwelling, accessory authorized ohana dwelling, or guest house. Properties with multi-family dwellings, or which are part of a planned development housing, cluster, or group living facility are also not eligible
  • Are owners required to live on the property? Yes, either the ADU or primary dwelling unit must be occupied by the property owner(s), or persons who are related by blood, marriage, or adoption to the property owner(s), or designated authorized representative(s), except in unforeseen hardship circumstances (i.e., active military deployment, serious illness).
  • Is there a minimum occupancy period for an ADU? Yes, an ADU may not be occupied for less than a six month (180 days) period.
  • Is there enough sewer and water capacity to accommodate ADUs? Sewer and water capacity varies from location to location. To assure the adequacy of the existing infrastructure, prospective applicants will need to receive confirmation from all appropriate agencies (The Department of Planning and Permitting’s (DPP) Customer Service Division; Wastewater Branch; and Traffic Review Branch, State Department of Health, Board of Water Supply, and Honolulu Fire Department), affirming the capacity of needed infrastructure. The DPP has developed a step-by-step Public Facilities Pre-Check Form for homeowners or contractors to get the required approvals. No building permit for ADUs shall be issued unless there is adequate infrastructure to support it.
  • Is parking required for an ADU? The ADU law requires one parking space to be located on the lot per ADU, in addition to the required parking for the primary dwelling unit. Tandem parking and compact stalls are permitted. However, ADUs within one-half mile of a rail transit station do not require parking. 

The above information was taken from the City's website here, or download the info sheets below: