For decades, a backyard cottage in Washington was a rental asset — never a saleable one. That changed with HB 1337 and the unit-lot subdivision reforms now rolling through Seattle, Tacoma, Bellevue and unincorporated King County. In 2026, a growing number of homeowners can legally split their lot, give their DADU its own title, and sell it to a separate buyer. Here is the 2026 playbook — what the law actually says, the step-by-step process, the real numbers, and when it is (and isn't) worth doing.
The Legal Foundation: HB 1337, HB 1110, and Unit-Lot Subdivision
Washington's HB 1337 (2023, fully in force in 2026) requires cities in urban growth areas to allow at least two ADUs per residential lot and prohibits owner-occupancy mandates. HB 1110 layered on middle-housing requirements that pushed cities to streamline lot splits. The key unlock for selling a DADU is the unit-lot subdivision: a recorded short plat that carves the parent lot into a primary-house lot and a separate DADU lot, each with its own legal description, address, and title.
Seattle's DCI began accepting unit-lot subdivisions for DADUs in 2024; Tacoma, Bellevue, and most of unincorporated King County followed in 2025. The result: a 750 sq ft DADU built in 2022 as a rental can, in 2026, be platted, refinanced separately, and sold to a first-time buyer — often for $400,000–$650,000 depending on the city.
The 7-Step Process to Sell a DADU Separately
- Feasibility review — confirm your zone allows unit-lot subdivision and that your DADU meets independent-utility, setback, and access requirements. 2) Survey and short-plat application — a licensed surveyor records new lot lines; the city assigns a new address. 3) Utility separation — water, sewer, power, and gas must each have an independent meter and shutoff serving only the DADU. 4) Easements — record cross-access, drainage, and shared-wall easements where needed.
- Final plat recording with the county auditor — this is the moment the DADU becomes its own legal parcel. 6) Title and lender package — order a new title commitment and, if you have a mortgage on the parent property, get a partial release from your lender. 7) List and close — the DADU can now be sold like any single-family home, financed with conventional, FHA, or VA loans depending on the buyer.
Real Numbers: Cost, Timeline, and ROI in 2026
Hard costs to subdivide a DADU in Puget Sound run roughly $18,000–$45,000: survey ($3,500–$6,000), short-plat fees ($4,000–$9,000 depending on city), utility separations ($6,000–$20,000 — by far the biggest variable), legal and title ($2,500–$5,000), and lender release fees ($500–$2,500). Timeline is 4–9 months from feasibility to recorded plat in most King County jurisdictions.
The payoff is significant. A turnkey 750 sq ft Seattle DADU that cost $260,000 to build typically appraises as a standalone home at $475,000–$575,000 in 2026 — a $200,000+ uplift over its value as an attached rental on the parent parcel. In Bellevue and Kirkland, separated DADUs have closed above $625,000.
When It Makes Sense — and When It Doesn't
Subdividing is the right move when your DADU is fully independent (no shared walls or shared mechanicals), your lot is large enough to meet minimum-area rules after the split, and you want to free up capital without selling the primary home. It is the wrong move if your DADU shares a foundation or roof with the main house, if the parent mortgage cannot be partially released, or if your rental income on the DADU exceeds 7% net yield — in that case, holding usually beats selling.
Three Puget Sound Scenarios We're Seeing in 2026
Seattle (Ballard): a 2021-built 720 sq ft DADU on a 5,200 sq ft lot subdivided in 7 months for $31,000 in soft costs; sold in May 2026 for $539,000. Bellevue (Crossroads): a 2023 DADU on a sloped 7,800 sq ft lot subdivided in 9 months ($42,000 in costs including a new sewer lateral); listed at $645,000. Tacoma (North End): a 2020 garage-to-DADU conversion subdivided in just 4 months under Tacoma's pre-approved short-plat track for $22,000; sold to a first-time buyer for $389,000.
Thinking About Subdividing? Start With Feasibility.
Every lot is different, and the difference between a 4-month and a 12-month subdivision is almost always discovered in the first feasibility review. Our permitting team has guided 11 DADU unit-lot subdivisions across Seattle, Bellevue, Tacoma, and unincorporated King County since 2024. If you are considering a sale — or just want to know what your DADU could be worth as its own parcel — we will run the feasibility for free.
Selling a DADU separately is no longer theoretical in Washington — it is happening every week. The homeowners moving first are unlocking real liquidity. Book a free feasibility review and we'll tell you exactly what your lot can do.