Accessory Structures in Tacoma, WA: What Residents Actually Need to Know

If you live in Tacoma or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Tacoma has 4 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

Tiny Homes

Tacoma normally requires manufactured homes built as two sections at least 12 by 36 feet each, but structures meeting IRC Appendix Q tiny-home standards skip that minimum-size rule.

Key details: Standard minimum: two 12x36-ft sections. Tiny homes: exempted from that minimum. Still required: permanent HUD-standard foundation. Standard source: IRC Appendix Q via State Building Code.

A manufactured or tiny home meeting neither the standard two-section size minimum nor the IRC Appendix Q exception is a Building Code violation subject to permit denial by the Building Official.

ADU Rules

Tacoma allows two accessory dwelling units per residential lot, each capped at 1,000 square feet of habitable area, with no parking required.

Key details: ADUs per lot: 2 allowed. Habitable area cap: 1,000 sq ft. Parking: None required. ADU-specific height limit: None (follows housing type).

Building without a permit or exceeding the 1,000-square-foot habitable-area cap can result in a stop-work order and code enforcement action under Title 13's ADU standards.

Shed & Carport Rules

Tacoma caps accessory buildings like sheds at 1,000 square feet, or 15% of lot area, and requires they sit behind the main house and out of side-yard setbacks.

Key details: Max footprint: 1,000 sq ft (or 15% of lot). Footprint cap vs. house: no more than 85% of house. Location: must sit behind front wall line. Garage doors: 20-ft setback from street. Interior use: no habitable space allowed.

Sheds exceeding the size cap or built into a required setback are zoning violations subject to code enforcement, correction orders, or removal under Title 13's Land Use Permits and Procedures chapter.

Garage Conversions

Tacoma allows homeowners to convert an existing garage or other accessory structure into a legal dwelling unit without meeting current setback, height or location standards, as long as it meets Building Code.

Key details: Structure must predate: February 1, 2025. Exempt from: setback, height, location rules. Still required: current Building Code compliance. Counts toward: 2-ADU-per-lot limit.

Converting without a building permit and City inspection bypasses the Building Code and zoning/minimum-and-maximum-size review Tacoma requires before occupancy, exposing the owner to code-enforcement action.

The Bottom Line

Tacoma's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Tacoma is broadly strict or permissive.

All of the above reflects Tacoma's municipal code as of our last review. If you need specifics on fines, exemptions, or filing requirements, the detailed ordinance pages linked above have the full breakdown.