Kauai County, HI Accessory Structures: Tiny Homes (2026)

Kaua'i County Code Section 12-2.4, Tiny Houses, incorporates Appendix Q of the 2018 International Residential Code for One- and Two-Family Dwellings by reference, subject to one local amendment. That amendment rewrites Section AQ102, Definitions, so that a Tiny House means a dwelling of 500 square feet or less in floor area, excluding lofts. The 500-square-foot ceiling is defined precisely: it is the sum of the horizontal areas of each floor of the building, measured from the interior faces of the exterior walls, and it includes enclosed attached accessory space such as a garage or storage area counted toward that total.

Unenclosed attached features, including carports, breezeways, lanais and porches, are excluded from the floor-area count, so a covered lanai will not push a home over the 500-square-foot line. Because Appendix Q is a set of alternative construction provisions rather than a separate permitting track, a Tiny House built to Appendix Q still goes through the same Building Division plan review and permit process as any other dwelling, and it must also satisfy the Comprehensive Zoning Ordinance's lot, setback and accessory-dwelling rules for wherever it is sited, whether as a principal residence, an accessory dwelling unit or a farm dwelling.

The ordinance was adopted by Ordinance No. 1163 on October 10, 2024, giving Kaua'i homeowners a code-recognized path to build smaller than a conventional single-family home without a separate variance for reduced floor area.