Accessory Dwelling Units

Accessory dwelling units (ADUs) are an important solution to the affordable rental housing crisis in Hawaii. Accessory dwelling units are small, separate living areas with their own kitchen, bathroom, and sleeping space that can be built on single family lots and may be attached or detached from a main house. To read the entire report, click here.

Why ADUs?

ADUs create rental housing: On Oahu, the greatest need is for affordable rental housing, but the private market has failed to create rental units. ADUs are a straightforward way to add to our affordable rental housing inventory without government subsidies, since homeowners cover the cost of development. The rents charged for ADUs are often affordable to low and moderate income renters.

ADUs provide a flexible housing option: Secondary units have long been used on Oahu as ohana dwellings and are ideal for intergenerational living. But while ohana units help adult children and aging parents to afford rental housing, the ban on rentals to non-relatives means that ADUs are limited in their usage.

Allowing rentals to non-family members will ensure that ADUs benefit homeowners in all phases of life, including when they do not have family members in need of housing but still need stabilizing income. This also adds units into the general housing stock. Greater flexibility will encourage ADU production because homeowners know that they and future owners can use them long-term.

ADUs help homeowners afford their homes: ADUs provide an additional source of income, helping homeowners afford their own homes—they are better able to pay their mortgages, property taxes, and other expenses.

ADUs enable aging in place: Rental income supports elders on fixed incomes, helping them to stay in their homes. ADUs can house caregivers and promote safety by having another person live on-site.

ADUs promote sustainability: They help to prevent urban sprawl while still maintaining neighborhoods’ character, and because of their smaller size, they use less energy.

ADUs support the local economy: Developing ADUs creates work for local builders and contractors, increases sales of construction materials, and provides ongoing government support through property taxes.

Regulated ADUs benefit tenants and the community: Allowing and regulating ADUs will promote units that are code-compliant and that owners pay relevant fees, such as sewer fees, and GET on rental income.

The lack of truly affordable housing for low-income residents of Hawaii is central to the economic hardships they face. We see the results of this struggle all around us in the eyes of our homeless population living in our streets and parks. Hawaii has the ninth highest rate of poverty in the nation and the highest rate of homelessness among states. The cost of shelter is the highest in the country, and 73% of our residents living below the poverty guidelines are spending more than half of their scarce resources on rent. We will need more than 19,000 more rental units by 2016 to meet the need for low-income households, yet the housing market is not building affordable rentals.

There are no easy answers to the dilemma we are confronting, but one statistic provides an important direction. Nationally, households have been getting smaller even while the size of housing units has dramatically increased. This trend holds true in Hawai‘i, where almost one out of four households are composed of single individuals. At the same time, our population is rapidly aging and living on fixed incomes, while young adults are often hard pressed to find affordable shelter.

Accessory Dwelling Units (ADUs) are small, separate living areas with their own kitchen, bathroom, and sleeping space that can be built on single family lots and may be attached or detached from a main house. ADUs provide an immediate economic incentive for private property owners to create more affordable rental housing at a minimal cost to the state and counties by using their existing lot or reconfiguring their existing home to build a secondary dwelling. Some of the benefits for private landowners investing in the creation of ADUs rental are obvious:

The benefits to our community are also clear:

  • The inventory of small units available to singles and small families will increase, freeing up larger units for bigger households
  • ADUs are small units that will have a limited impact on existing infrastructure, and reduce environmental impacts by helping prevent urban sprawl
  • No government subsidies are required as private landowners respond to the demand for rentals and opportunities for income

There are already jurisdictions in Hawai‘i that permit secondary units. Around the country, communities have successfully used ADUs as a vehicle for addressing the limited supply affordable rental housing:

  • On Kauai, one additional single-family dwelling unit can be built on any lots zoned for single family homes
  • On Maui, only one additional parking space is required and occupancy is not restricted to relatives
  • On Oahu, in addition to ohana housing, rules provide that lot sizes of 7,500 square feet and above can have up to 2 attached units while a 10,000 square foot lot can have 2 detached units.
  • In Portland, Oregon, ADUs are allowed in all residential zones with no minimum square footage or additional parking spaces required
  • Lexington, Massachusetts allows for up to 2 ADUs per lot and only one additional parking space is required
  • Santa Cruz, California developed a program that has facilitated the creation of ADUs by providing model plans, technical assistance, and expedited permitting process along with an ADU manual to guide interested landowners

ADUs can help address our need for affordable rentals if:

  • County building ordinances that control the creation of ADUs are relaxed
  • Amnesty programs are implemented to allow the legal conversion recreation room illegally used as rentals
  • Restrictions limiting ohana rentals on family member occupancy are lifted
  • Pre-approved model ADU plans are developed and made available to homeowners to facilitate the speedy approval of new units

Taking these steps will allow private landowners to be a part of the solution for our state’s housing crisis while keeping the management of land use and infrastructure within local control.

To read the full report, click here.
To see Star-Advertiser's article on ADUs, click here.
For additional information on ADUs in Hawai‘i, see Questor Lau’s website here.
Click here to read more about our work with affordable housing in Hawaii.