Garage Conversions: Honolulu vs Mililani Town
How do garage conversions rules compare between Honolulu, HI and Mililani Town, HI?
Honolulu has fewer restrictions than Mililani Town.
Honolulu, HI
Honolulu County
Honolulu's LUO § 21-5.720 allows garage and accessory structure conversions into accessory dwelling units in residential zones, subject to floor area limits, parking requirements, and a building permit from DPP.
View full Honolulu rules →Mililani Town, HI
Honolulu County
Garage conversions in Mililani Town are regulated as ADUs under ROH Sec. 21-5.720 and commonly prohibited or restricted by HOA covenants, requiring both city permits and association approval.
View full Mililani Town rules →Key Facts Comparison
| Fact | Honolulu | Mililani Town |
|---|---|---|
| Minimum lot size | 3,500 sq ft | - |
| Max ADU size (small lot) | 400 sq ft (3,500–4,999 sq ft lot) | - |
| Parking requirement | 1 space per ADU (may be waived) | - |
| Transit waiver radius | Within 0.5 mile of rail station | - |
| Governing section | LUO § 21-5.720 | - |
| - | - |
Highlighted rows indicate differences between cities.
Honolulu FAQ
Can I convert my garage to a rental unit on Oahu?
Yes, if your lot is at least 3,500 sq ft in a residential zone and you owner-occupy the property. You need a building permit from DPP and must meet floor area, parking, and building code requirements under LUO § 21-5.720.
Do I need to add a parking space when converting my garage to an ADU?
Generally yes, one additional off-street parking space is required. It may be waived if your lot is within 0.5 miles of a Honolulu rail station or if topography makes parking infeasible per DPP.
Are there any fee waivers for ADU conversions?
Starting July 1, 2025, qualifying ADU projects are exempt from certain wastewater system facility charges. Regular building permit fees based on project value still apply.
Mililani Town FAQ
Can I convert my Mililani garage into a bedroom?
Check your HOA CC&Rs first. Many Mililani associations prohibit garage conversions. If allowed, a city building permit and ADU compliance are still required.
What if my neighborhood allows it but parking is tight?
You will need to provide replacement parking on your lot that meets city standards and often HOA surface and placement rules.
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