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Building an ADU? Three Things You Need to Know

It’s been almost a year since our first post on the difference between Ohana and Accessory Dwelling Units.  Given that ADU construction remains one of the most common residential construction projects in Hawaii, we thought it was time to follow-up with more information for homeowners considering the ADU process.  Here are three things you should know about building an ADU:

  • There are very specific regulations regarding ADU construction in Hawaii. You can read the entire Bill legalizing ADU’s online, but the knowing the basics is a great start. In order to build an ADU, your lot must be zoned in a residential or country district, and be at least 3,500 square feet.  ADU’s can only be built on properties with a pre-existing single-family residence, and the owner must provide an additional parking space and road access for ADU residents. Furthermore, the property owner or family member must continue to live on the property, and must lease or rent the ADU for increments of at least six months. Lastly, ADU’s are intended to be small-scale residential builds. For a 3,500 square foot property, the ADU cannot exceed 400 square feet- or 800 for lots with a square footage of 5,000 or more.


  • ADU’s can serve multiple purposes, so it is important to design the residence in a way that fits your needs. An ADU designed for a series of long-term renters (remember, the minimum lease period is six months,) will have different requirements than a home designed for multigenerational family use. While some renters might love sleeping in a loft-style master bedroom, you may need a different floor plan to accommodate grandparents or families with small children.


  • You still benefit from working with professionals. Despite its small size, an ADU is still a major home construction project. Working with an architect and contractor may seem like an unusual investment for a 400-square-foot home, but working with an expert can save you money: the right architect will help you create an energy efficient home built with materials that are both durable and cost-efficient. And since smaller home designs come with unique challenges in terms of electrical, plumbing, and utilities maintenance, finding a good contractor will ensure that your ADU maintains its value as a residence and potential secondary income.

Ready to find the architects and professionals you need to design and build your Accessory Dwelling Unit? Want more information on how much an ADU will cost? Contact us today for assistance in locating the right professionals in your area. You can also use our free online project estimator to help you begin the budgeting process. Happy building!

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