Can I Build ADU in Honolulu, HI? (2026)
Find out if you can build a adu in Honolulu, HI. Rules, permit requirements, costs, and next steps.
Yes, ADUs are allowed in Honolulu, HI. California state law ensures by-right approval.
An Accessory Dwelling Unit (ADU) is a secondary housing unit on a residential lot — also called a granny flat, in-law suite, or backyard cottage. In Honolulu, HI, ADUs are permitted by right under state law, making them one of the most accessible ways to add housing on your property. ADUs can be detached, attached to the main home, or created by converting an existing garage or accessory structure.
ADU Rules in Honolulu
ADU Rules in Honolulu: Detached ADU max size: 400 sq ft. Attached ADU max size: No greater than 50% of primary dwelling floor area. Setbacks: 5 ft side, 5 ft rear. Owner-occupancy: Owner-occupancy requirement eliminated statewide per Hawaii Act 232 (2023). Neither the primary dwelling nor the ADU must be owner-occupied.. State preemption applies: HI law requires Honolulu to approve compliant ADUs by right.
Costs & Fees
ADU permits in Honolulu: Total estimated permit cost: $5,000–$15,000 total fees depending on size and scope. Contact the Honolulu Department of Planning and Permitting (DPP) for current fee schedule.
Timeline
Honolulu DPP building permit: typically 6-12 weeks plan check. Honolulu is known for slower permit processing. Construction typically 6-18 months. Act 232 requires ministerial approval for qualifying ADUs meeting objective standards.
Next Steps
Next steps for building an ADU in Honolulu: 1. Review full ADU rules including size limits, setbacks, and parking. 2. Apply for an ADU permit through the Honolulu Department of Planning and Permitting (DPP) at https://www.honoluludpp.org/Permitting. 3. Hire a licensed contractor familiar with HI ADU requirements.
Honolulu Department of Planning and Permitting (DPP)
Phone: (808) 768-8000
Website: https://www.honoluludpp.org/
Online Permits: https://www.honoluludpp.org/Permitting
Frequently Asked Questions
Can I build an ohana unit (ADU) on my Honolulu property?
Yes. Hawaii Act 232 (2023) requires Honolulu to permit ADUs (called 'ohana dwelling units' locally) by right on single-family lots, with ministerial approval for code-compliant applications. Owner-occupancy requirements were eliminated statewide. The permit process is through Honolulu DPP. Honolulu is known for slower permit processing — plan for 6-12 weeks for plan check.
What is an ohana unit and how does it differ from a California JADU?
An ohana unit is Honolulu's term for an accessory dwelling unit — 'ohana' means family in Hawaiian. Unlike California's JADU (Junior ADU), which is specifically defined in California Government Code and is a California-only concept, Honolulu's ohana unit is a full ADU. Honolulu's ohana unit rules historically required owner-occupancy (now eliminated by Act 232) and were focused on housing extended family. The JADU concept from California does not apply in Hawaii.
Why are short-term rentals so restricted in Honolulu?
Honolulu has some of the strictest STR regulations in the US. A 2019 ordinance severely limited new Transient Vacation Unit (TVU) permits — new TVU permits are generally only available in resort-zoned areas like Waikiki and Ko Olina. Residential neighborhoods are largely closed to new STR applicants. Violations carry fines up to $10,000 per day — among the highest in the nation. This reflects community concerns about housing affordability and neighborhood character in Hawaii.
Does Hawaii have a solar mandate?
Yes — for solar water heating. Hawaii law (HRS Section 196-6.5) requires solar water heating systems on all new single-family residential construction unless a cost-effectiveness waiver is granted. This is one of the few states with a solar mandate. Additionally, Hawaii has some of the highest electricity rates in the US ($0.38+/kWh), making solar PV economically very attractive. Over 25% of Honolulu single-family homes have solar.
Is Honolulu city or county?
Both. The City and County of Honolulu is a consolidated city-county government governing the entire island of Oahu — including urban Honolulu, Waikiki, Pearl City, Kailua, Kaneohe, and all other communities on Oahu. The Honolulu Department of Planning and Permitting (DPP) handles all building permits, zoning, and planning for the entire island.
What is the Special Management Area (SMA) and does it affect my property?
The Special Management Area (SMA) is a coastal zone designation covering properties near Oahu's shoreline, administered under Hawaii's Coastal Zone Management Program. If your property is in the SMA (generally within 100-300 ft of the shoreline), certain development activities require an SMA permit in addition to standard building permits. The SMA is designed to protect Hawaii's coastal resources. Check with Honolulu DPP at honoluludpp.org for SMA boundary information.
Source: Honolulu Department of Planning and Permitting (DPP) — Building Regulations. Last verified April 6, 2026. View source