Executive Summary

Accessory dwelling units (ADUs) are an important tool in expanding affordable housing stock, especially in areas with limited room for growth and high housing costs. This policy brief describes ADUs and their benefits and provides examples of successful ADU policies from around the country. This brief concludes with initial proposals for policies, initiatives and reforms that would balance the needs and concerns of communities while allowing and facilitating ADU creation.

Background

Accessory dwelling units are separate living areas with their own kitchen, bathroom and sleeping facilities. ADUs are built on a single-family lot and may be inside, attached, or detached from the main house. They can be created by converting or adding to an existing home or garage, or constructed as a new separate building on the lot.

While accessory dwelling units go by a variety of names, including granny or mother-in-law flats, in Hawaiʻi they are best known as “ʻohana units,” emphasizing their unique history here and the importance of intergenerational living. For clarity, this brief will refer to such units as accessory dwelling units (ADUs) unless specifically referring to ADUs whose occupancy is limited to family members, such as ʻohana units on Oʻahu.

Nationally, households have been getting smaller, yet the size of housing units has dramatically increased. This trend holds true in Hawaiʻi. One out of four households in Hawaiʻi are now composed of a single individual. Our population is also rapidly aging, while young people are often hard-pressed to afford the high cost of living in Hawaiʻi.

At the same time, the cost of living continues to rise, including the cost of shelter, which is twice the national average. Not only do we have the highest single family home prices in the nation, but we also face the highest rents. Rents have increased 45 percent between 2005 and 2011 alone, and 75 percent of extremely low-income households are paying more than half of their income in rent.

This dramatic shortfall in affordable housing is a major reason why Hawaiʻi has the highest rate of homelessness among the states. This crisis can only be resolved with an adequate stock of affordable housing for our entire community. Accessory dwelling units are a promising strategy that engages the private sector to create more affordable rentals at minimal cost to the state and counties.