Hawaii now requires all four counties to allow multiple ohana/ADUs per lot — a major shift; the building runs through county codes and shipping is the cost driver.
Building approval
County building departments (4 counties)
Program
County codes (modular = 75%+ off-site) — Home rule — national code, locally enforced
ADU law
SB 3202 (2024); Act 232 (2023); Honolulu Ord 25-2 (2025) (statewide)
ADU summary
All counties must allow ≥2 ADUs/lot; owner-occupancy eliminated statewide.
Site / structural drivers
Hurricane wind, salt/corrosion, seismic (Big Island); shipping
Verdict
Statewide ohana/ADU expansion
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General information, current as of 2026 — not legal advice. Confirm specifics with your local jurisdiction.
More than before. SB 3202 (2024) requires all four counties to allow at least two ADUs per residential lot. In Honolulu, Act 232 (2023) requires the city to permit ADUs ('ohana dwelling units') by right on single-family lots with ministerial approval, and Ordinance 25-2 (effective September 30, 2025) further expands options — even some sub-3,500 sq ft lots can add a 500 sq ft ADU. Hawaii County's Bill 123 allows up to three ohana units/ADUs on a qualifying lot. Owner-occupancy requirements were eliminated statewide. Confirm your county's current rules.
Each of the four counties (Honolulu, Hawaii, Maui, Kauai) administers its own building code. A modular home — defined as a dwelling 75% or more constructed off-site — is built to the applicable county code and assembled on a permanent foundation by licensed local contractors (in-state programs like HPM's HalePlus build to County of Hawaii codes). Your county permits the installation and site work.
Two things dominate. First, logistics — most materials and many modular units come from the mainland by ocean freight, so shipping is a significant cost and schedule factor; in-state factory programs help. Second, the environment — high wind (hurricane exposure), salt air and humidity (corrosion-resistant detailing), seismic activity (especially the Big Island), and flood/tsunami and lava-zone considerations all shape the design. PSL Modular engineers the envelope and plans the logistics.
Yes — owner-occupancy requirements for ADUs were eliminated statewide, which (along with the two-ADU minimum under SB 3202) makes ohana units a much stronger option for both multigenerational living and rental income. Each county still sets size, setback, and infrastructure standards, so confirm locally.
Yes — Hawaii has some of the highest housing costs in the country and a deep cultural tradition of ohana (multigenerational) units, and the 2024-25 laws opened the door wide. Modular delivers a finished, code-compliant unit faster than site-built in a high-cost labor market. The main planning items are shipping and the island-specific envelope.
PSL Modular units are permittable in all 50 states. Pick yours for the building-approval path, the ADU law, and the structural spec your site needs.