Can I Build Tiny Home in Seattle, WA? (2026)
Find out if you can build a tiny home in Seattle, WA. Rules, permit requirements, costs, and next steps.
Tiny homes on permanent foundations are allowed in Seattle, WA. Tiny homes on wheels are not permitted as permanent dwellings.
A tiny home is a small dwelling unit — typically under 400 sq ft — that can be built on a permanent foundation or on wheels. In Seattle, WA, the rules differ significantly depending on whether the structure is on a permanent foundation (treated as a dwelling unit under building code) or on wheels (treated as a recreational vehicle under vehicle code). Tiny homes on permanent foundations must meet a minimum size of 150 sq ft in Seattle.
Tiny Home Rules in Seattle
Tiny Home Rules in Seattle: Foundation-based tiny homes: Permitted. Tiny homes on wheels (THOWs): Not permitted as permanent dwelling — classified as recreational vehicle. Minimum size: 150 sq ft. Tiny homes on permanent foundations must meet Seattle Residential Code minimum habitable space requirements (minimum room size 70 sqft, minimum ceiling height 7 ft). Tiny homes on wheels (THOWs) are not permitted as permanent dwellings in Seattle residential zones — classified as recreational vehicles. Seattle has addressed homelessness with sanctioned encampments in some areas but THOWs are not permitted as permanent dwelling units in residential zones. Tiny homes on foundations may qualify as DADUs if they meet SMC 23.44.041.
Costs & Fees
Building permit fees for tiny homes in Seattle follow the same schedule as other new construction. Contact the Seattle Department of Construction and Inspections (SDCI) at (206) 684-8850 for current fee information.
Next Steps
Next steps for building a tiny home in Seattle: 1. Determine foundation vs. wheeled — the rules are fundamentally different. 2. For foundation tiny homes, obtain a building permit from the Seattle Department of Construction and Inspections (SDCI). 3. For wheeled tiny homes, verify whether your property allows RV siting. 4. Check if your tiny home could qualify as an ADU on your property.
Seattle Department of Construction and Inspections (SDCI)
Phone: (206) 684-8850
Website: https://www.seattle.gov/sdci
Online Permits: https://cosaccela.seattle.gov/portal/welcome.aspx
Frequently Asked Questions
Can I build an ADU (backyard cottage) in Seattle?
Yes. Seattle is one of the most ADU-friendly cities in the US. You can build both a Detached ADU (backyard cottage/DADU, up to 1,000 sqft) and an Attached ADU (up to 1,000 sqft) on the same lot — 2 ADUs total per Washington HB 1337. No owner-occupancy requirement. No additional parking required. Building permit from Seattle SDCI required. Pre-approved standard DADU plans are available to speed up the permit process.
What changed in Seattle's ADU rules because of Washington HB 1337?
Washington HB 1337 (effective July 2023) codified what Seattle had already done in 2019: allows 2 ADUs per single-family lot, removes owner-occupancy requirements, and eliminates parking mandates near transit. Seattle was a national leader in ADU reform before HB 1337. The state law now ensures that other Washington cities must follow Seattle's example. Seattle's existing ADU ordinance continues to govern locally.
Do I need a permit for a home business in Seattle?
No city-issued permit is required to operate a qualifying home occupation in Seattle. You may work from home as long as you have no client visits, no non-resident employees working on-site, no external evidence of the business, and your business use is incidental to the residential use. You will need a Seattle business license and a Washington State business license regardless. Cottage food operations (baked goods, jams, etc.) require Washington Dept of Agriculture registration.
Can I do short-term rentals on Airbnb in Seattle?
Yes, with a Short-Term Rental Operator's License (approximately $75/year). If you live on-site (operator-occupied), you may rent your home for an unlimited number of nights annually. Airbnb automatically collects and remits Seattle and Washington lodging taxes (combined approximately 15.6%). Display your license number on your listing. Operating without a license carries fines of $500+ per violation.
What are the setbacks in Seattle's SF 5000 zone?
In Seattle's SF 5000 zone (most common single-family zone), the front setback is 20 feet, side setbacks are 5 feet on each side, and the rear setback is typically 25 feet (20% of lot depth, minimum 20 ft, maximum 25 ft). Maximum lot coverage is 35% (plus additional allowance for DADUs). Maximum building height is 30 feet. Verify your specific parcel using SDCI's parcel data tool — shoreline, environmental overlay, or historic designation may add requirements.
Is solar required on new homes in Seattle?
No. Washington does not have a statewide new-construction solar mandate. Seattle encourages solar through streamlined permitting and incentive programs, but it is not required. Seattle City Light offers net metering and the federal Investment Tax Credit (ITC) reduces solar installation cost by 30%. Standard residential solar permits are processed quickly through SDCI.
How do I look up the zoning for my Seattle property?
Use SDCI's Parcel Information tool at seattle.gov/sdci/permits/do-i-need-a-permit/parcel-information. Enter your address to find your zoning designation, ADU eligibility, lot size, and any overlays (environmental critical areas, shoreline, landmark, flood zone). You can also view Seattle's interactive zoning map at https://www.seattle.gov/opcd/ongoing-initiatives/seattle-2035.
Source: Seattle Department of Construction and Inspections (SDCI) — Building Regulations. Last verified April 5, 2026. View source