Tiny home rules in Costa Mesa, CA — covering tiny houses on wheels (THOWs), park model RVs, and tiny home on foundation builds — determine where they are legal and how they get permitted.
Costa Mesa permits foundation tiny homes as Accessory Dwelling Units under CMMC Title 13 and California Government Code Section 65852.2, which preempts most local restrictions for ADUs up to 1,200 sq ft. California Residential Code Appendix AX (effective 2023) sets construction standards for tiny houses on permanent foundations 400 sq ft or less. Tiny houses on wheels are classified by HCD as recreational vehicles.
Costa Mesa Municipal Code Title 13 implements California Government Code Section 65852.2, which preempts most local restrictions for Accessory Dwelling Units at or under 1,200 square feet and limits side and rear setbacks for new detached ADUs to 4 feet. Junior ADUs are limited to 500 square feet under Government Code Section 65852.22, are permitted only on lots with a single-family dwelling, and require owner occupancy. A foundation tiny home can be permitted as an ADU; the 2022 California Residential Code Appendix AX sets standards for tiny houses 400 square feet or less, including loft, ladder, and ceiling-height rules. A tiny house on wheels is treated by California HCD as a recreational vehicle built to ANSI A119.5 standards and requires DMV registration; Costa Mesa has not published a movable tiny house ordinance authorizing them as primary residences. AB 2533 (Government Code 66332), effective January 2025, is an ADU amnesty law for legalizing existing unpermitted ADUs and does not authorize movable tiny houses. Confirm any project with the Costa Mesa Planning Division.
Siting a tiny house on wheels as a permanent residence without a permit can be cited as an unpermitted dwelling under CMMC Titles 5 and 13 and may require removal. A foundation tiny home that exceeds ADU size, setback, or height standards is enforceable through Costa Mesa Code Enforcement.
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Side-by-side rule comparisons with other cities in Orange County.
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See how Costa Mesa's tiny homes rules stack up against other locations.
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