Can you sell an ADU separately as a condo in Washington?

Short answer: yes, through a condominium. Washington’s 2023 ADU law says a city or county may not prohibit the sale of a condominium unit separately from the main house just because it was originally built as an ADU (RCW 36.70A.681(1)(k)). In July 2026, Division I of the Court of Appeals relied on that rule in Ladder Properties LLC v. City of Snoqualmie, holding that a city cannot penalize owners for recording a condominium declaration on lawfully built ADUs.

What the law does not do is split your lot for you. An ADU cannot simply get its own deed. The property has to become a small condominium: two units, plus land and systems owned in common.

What “selling it as a condo” actually means

After the conversion, the main house is Unit 1 and the ADU is Unit 2. Each owner owns their unit outright and a share of the common elements: the land, the driveway, shared pipes. A two-member owners’ association decides on shared costs such as a sewer repair. Each unit can be sold, mortgaged and inherited on its own.

The four things it takes

1. A declaration recorded with the county under Washington’s condominium act (RCW 64.90), defining the units, common elements and rules.
2. A map of the units and common elements; when it is a survey, a licensed surveyor makes it.
3. Separate utilities, in practice at least: each unit with its own electric and water meter, and a side sewer arrangement the declaration spells out.
4. A lender who will finance the unit. Buyers need a condominium mortgage, and very small condominiums can raise questions with some lenders and loan programs. Ask before you commit.

What can still stop it

• Private covenants. CC&Rs already recorded on your lot are not overridden by the ADU law.
• Your current mortgage. Your lender has to consent, because the conversion changes the collateral.
• Critical areas. The state ADU rules do not apply on lots with designated critical areas or their buffers.

Is it worth it?

It can be, if you want to sell the ADU to family, release equity without selling the house, or build to sell. It is less attractive if you plan to keep both homes: you take on legal, survey and association costs and a neighbor-owner for good. The decision is easiest to make before design, because separate services are cheap to build in and expensive to add later.

The full process, step by step, is in our guide Selling an ADU as a condo.