Accessory Structures in Kauai County, HI (2026)

ADU Rules

Kauai County uses three distinct accessory dwelling categories under its Comprehensive Zoning Ordinance (CZO), Kauai County Code Chapter 8: an Additional Dwelling Unit (ADU), an Additional Rental Unit (ARU), and a Guest House. ADUs and ARUs are permitted only in Residential (R) districts on lots with one principal single-family dwelling; Guest Houses are allowed in Residential, Agricultural, Open, and certain other districts. ADUs have no size cap (lot coverage controls), require 2 off-street parking spaces, and must include a kitchen. ARUs are capped at 800 square feet, require 1 parking space, and must be used only for long-term rentals of at least six months. Guest Houses are capped at 800 square feet (raised from 500 sf by Bill 2933 in 2024) and may include a kitchen but cannot be used as short-term/transient rentals. ARUs are prohibited in tsunami evacuation zones west of the Hanalei River. Hawaii Act 39 (SLH 2024 / SB 3202), codified at HRS Section 46-4.8, requires each county to allow at least two accessory dwellings on residentially zoned lots by December 31, 2026; Kauai's existing ADU + ARU framework already satisfies that statutory floor.