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Looking to Build an Accessory Dwelling Unit in Hawaii?

An Accessory Dwelling Unit is the idea to add another unit on your property or attached to your existing house.

What is an Accessory Dwelling Unit? 

An accessory dwelling unit, or ADU, is an additional dwelling unit on an existing property that includes a full kitchen, a bathroom, sleeping area, and parking stall. ADUs can be used as rental units (rental period has to be at least 6 months ) or extra living space for you and your family. It can be a separate structure, an extension of a main house or a conversion of an existing structure.

Rendering of an ADU Kit from Hardware Hawaii

Tip! ADUs are not the same as ohana dwelling units. Ohana dwelling units are restricted to family members only and are subject to a maximum building area standard. 

What are the Benefits of ADUs?

  1. Increase rental housing supply. ADUs help to meet the high demand for rental housing and affordable homes in Hawaii
  2. Provides a source of income. Rental income from ADUs can help to pay for your mortgage, bills, or other expenses, as well as to add to your savings. 
  3. Supports local economy. You will help to support the construction industry and families in need of affordable homes. 
  4. Promotes sustainable living. ADUs help to reduce waste and are energy efficient.
  5. Minimizes urban sprawl. ADUs help to protect rural areas from development by allowing for additional housing in existing neighborhoods.
  6. Support aging in place. ADUs can provide accessible, single-level living to age in place. 

What are the Basic Requirements to Apply?

  1. Your property must be in a residential area or country district. (R-3.5, R-5, R-7.5, R-10, R-20)
  2. Your lot must be at least 3,500 square feet. 
  3. Your lot must contain at least one single-family dwelling
  4. The property owner (or property owner's family) must reside on the property. 
  5. Your property cannot be landlocked
  6. Homeowners must agree to not sell ADU or subdivide lot. 
  7. You must be able to provide a parking space.
  8. Homeowners must complete a restrictive covenant form

How do I Apply?

First, request approval from the Department of Planning and Permitting:

  • Complete a Pre-Check Form
  • Provide a copy of the floor plan and plot plan

With approval of the Pre-Check form, you will need to apply for a building permit online and have 4 copies of buliding plans to upload to ePlans. A restrictive covenant form must also be completed and submitted to the Permit Issuance Branch before building permit is issued.  

What are the Building Requirements?

Only one ADU per lot is permitted.

Lot Size (square feet)                                              Living Floor Area (square feet)

3,500-4,999                                                            400

5,000 or more                                                         800

Where Can I Find ADU Resources?

There are many options for building your new ADU in Hawaii. One of the most popular ways is ADU kits, or prefabricated modular homes. 

Companies specializing in Hawaii ADU Kit Homes:

Other Guides: 

Guide to Building an Accessory Dwelling Unit 

Contact the Honolulu Department of Planning and Permitting (DPP)