What counts as an ADU in Seattle?

An accessory dwelling unit is a second, self-contained home on a single-family lot: an attached ADU (AADU) inside or attached to the main house, or a detached ADU (DADU, a backyard cottage). Washington's 2023 law (HB 1337) required cities to allow two ADUs per lot and to drop owner-occupancy rules by mid-2025; Seattle's code follows it. The difference that matters when you buy is whether the unit was permitted and finaled as a dwelling, or is an unpermitted "in-law" space.

Does a permitted ADU in Seattle count toward my mortgage?

Often, yes. Conventional loans can count rental income from a permitted ADU when it is documented (a lease or an appraiser's rent schedule), and FHA counts a share of it. Unpermitted units get no credit, so the permit status changes what you can borrow. Your lender decides; your agent pulls the permit history before you write.

How do I check whether an ADU is legal before I buy in Seattle?

Three records: the city's permit history for the address (the ADU should show a dwelling-unit permit and a final inspection), the county assessor record (a legal unit is usually counted), and the listing's NWMLS remarks (agents must describe unpermitted space honestly, but "in-law suite" is not a permit). RexMont pulls all three during the inspection period.

Can I rent the ADU out in Seattle?

A permitted ADU can be rented long-term under the city's rental rules; short-term rentals are regulated separately, so confirm the current code before you count on nightly income. Many Seattle buyers use the ADU for family first, rent it later, or house-hack from day one.

How much more does a house with an ADU sell for in Seattle?

The twelve-month closings on this page are the answer for Seattle: compare the median here with the city median on the housing-market page. A permitted, separately metered unit with its own entrance commands the most; a basement with a hot plate does not. RexMont prices the two parts separately when we list one.

Seattle, WA · Homes with an ADU, DADU or in-law suite

Seattle homes with an ADU for sale

189 active NWMLS listings right now · 699 closed in the last 12 months at a median $950K. Refreshed hourly.

See the listings What is my ADU home worth?

This page lists every Seattle house on the NWMLS whose listing describes an ADU, a detached ADU (backyard cottage) or an in-law suite, refreshed hourly. 699 such homes closed in Seattle in the last twelve months at a median $950,000 ($550 per square foot, 10 median days on market). The value is in the permit: RexMont pulls the city's permit history and the rent record before you write, and prices the main house and the unit separately when you sell.

Written by Adriano Tori, Founder & Designated Broker · WA Lic. #27660Reviewed 2026-10-231,244+ five-star Google reviews

The last 12 months

What homes with an ADU sold for in Seattle, Oct 2025 to Oct 2026

Every closed NWMLS sale of homes with an ADU in Seattle in the window, compiled by RexMont from the listing records. This is the comparable set a buyer should be offering against and a seller should be pricing from.

Closed sales: 699
Median price: $950K
Median $/sq ft: $550
Median days on market: 10
Sale-to-list: 100.0%
Sold at or over asking: 57.1%

Sales by price

Under $750K175
$750K–$1M208
$1M–$1.5M172
$1.5M–$2M77
$2M–$3M52
$3M+15

Where they sold (NWMLS area)

Ballard/Greenlake179
West Seattle129
North Seattle104
Queen Anne/Magnolia66
Southeast Seattle64
Central Seattle61

Range $316K to $5.42M; median home 1,920 sq ft, median year built 1945.

Information and statistics derived from Northwest Multiple Listing Service. Window Oct 2025–Oct 2026; refreshed monthly.

How this market works

What a Seattle home with an ADU buyer is really buying

Seattle made the ADU legal to build and easy to finance before any other city in the state: since 2019 a lot may carry two accessory dwelling units, a detached unit may be up to 1,000 square feet, no parking space is required and the owner does not have to live on the property. Thousands of backyard cottages and basement apartments have been permitted since, and every one of them is a second home on a single-family lot.

The houses on this page are the ones whose listing describes an ADU, a DADU or an in-law suite. The word in the listing is not the permit. I pull the Seattle permit history for every one of these homes before a client writes, because a permitted, finaled unit with its own entrance is income a lender can count and a buyer will pay for, and an unpermitted basement with a hot plate is neither. When we list an ADU house, the permit file and the rent record are the brochure.

The twelve-month data on this page is every Seattle ADU-home closing on the NWMLS: where they sold, for how much, how fast.

New listing alerts

New Seattle homes with an ADU, the day they list.

Permitted ADU homes draw multigenerational buyers and investors at once. Add an email and a RexMont agent sends each new Seattle ADU listing as it hits the NWMLS, with the permit status checked first.

Watching: Seattle houses with an ADU, DADU or in-law suite

Seattle homes with an ADU for sale right now

Active NWMLS listings of homes with an ADU in Seattle (189 active). Refreshed hourly.

See every listing →

Based on information submitted to the MLS GRID as of October 23, 2026 at 2:25 AM PT (date and time MLS GRID Data was obtained). All data is obtained from various sources and may not have been verified by broker or MLS GRID. Supplied Open House Information is subject to change without notice. All information should be independently reviewed and verified for accuracy. Properties may or may not be listed by the office/agent presenting the information.

Listing information courtesy of Northwest Multiple Listing Service (NWMLS). The listing data relating to real estate for sale on this web site comes in part from the Northwest Multiple Listing Service. Real estate listings held by brokerage firms other than RexMont Real Estate are marked with the “Listing courtesy of NWMLS” designation. Information provided is for the consumer’s personal, non-commercial use and may not be used for any purpose other than to identify prospective properties consumers may be interested in purchasing.

Some IDX listings have been excluded from this website.

Where to look

Where Seattle ADU homes are

Ballard, Phinney Ridge and Greenwood

The highest density of permitted backyard cottages in the city, behind 1910s–20s bungalows on alley lots.

Wedgwood, View Ridge and Maple Leaf

Post-war houses with daylight basements converted to attached ADUs; larger lots for a DADU.

Beacon Hill, Columbia City and Rainier Valley

The best ADU value in the city: lots that take a cottage, near light rail, where the rent covers the most mortgage.

West Seattle

Deep lots in Fauntleroy, Gatewood and Arbor Heights take detached units; Admiral and the Junction carry basement ADUs.

Capitol Hill and the Central District

Carriage houses and basement apartments in 1900s houses; the highest ADU rents in the city.

Lake City and Northgate

Large 1950s–60s lots with room for a cottage; the most affordable entry to an ADU house.

Before you write

What to check before buying a Seattle home with an ADU

Permit history first

Pull Seattle's permit records for the address: a legal ADU shows a dwelling-unit permit and a final inspection. An "in-law suite" with a kitchenette and no permit is extra space, not a second home, and lenders treat it that way.

Separate entrance, separate meter, separate lease

The ADUs that rent well and appraise well have their own door, often their own utility metering, and a lease a lender can read. Ask for the current lease and the rent history when the unit is occupied.

Rental income on the loan

Conventional and FHA underwriting can count documented ADU rent toward qualifying. Decide early whether you need that credit; it changes which homes you can afford and which lender to use.

Short-term rental rules are separate

Long-term rental of a permitted ADU is allowed; nightly rental is regulated by Seattle separately. Count on long-term rent in the math and treat anything else as a bonus.

Who lives where

Since 2025 Washington cities may not require the owner to live on the lot, so an ADU house can be two rentals. Still, the best use for many buyers is family first: a parent, an adult child, a caregiver.

Resale is to a defined buyer

Houses with permitted ADUs sell to multigenerational families, house-hackers and investors. When you sell, the permit file and the rent record are the marketing. RexMont prepares both.

Selling

Selling a house with an ADU in Seattle?

The buyers for a house with an ADU search for exactly this page, and they compare your home with the closings listed above, not with the city median. RexMont prices from this set, prepares the file the buyer's inspector and lender will ask for, and markets to the audience that is already looking.

Adriano Tori, RexMont's founder and designated broker, prepares the value personally for every home in this niche: the closings, the current competition, and the number that gets the home sold, in writing, within one business day.

Your buyers are comparing you with the 699 homes with an ADU that closed in Seattle in the last 12 months, median $950K.

What is my home with an ADU worth?

Prepared by Adriano ToriFounder & Designated Broker · WA Lic. #27660

A written value within one business day.

The address, your timing, and anything you want us to know. Adriano prepares the value from the Seattle homes with an ADU closings and sends it in writing.

Common questions

Seattle homes with an ADU FAQ

What counts as an ADU in Seattle?: An accessory dwelling unit is a second, self-contained home on a single-family lot: an attached ADU (AADU) inside or attached to the main house, or a detached ADU (DADU, a backyard cottage). Washington's 2023 law (HB 1337) required cities to allow two ADUs per lot and to drop owner-occupancy rules by mid-2025; Seattle's code follows it. The difference that matters when you buy is whether the unit was permitted and finaled as a dwelling, or is an unpermitted "in-law" space.
Does a permitted ADU in Seattle count toward my mortgage?: Often, yes. Conventional loans can count rental income from a permitted ADU when it is documented (a lease or an appraiser's rent schedule), and FHA counts a share of it. Unpermitted units get no credit, so the permit status changes what you can borrow. Your lender decides; your agent pulls the permit history before you write.
How do I check whether an ADU is legal before I buy in Seattle?: Three records: the city's permit history for the address (the ADU should show a dwelling-unit permit and a final inspection), the county assessor record (a legal unit is usually counted), and the listing's NWMLS remarks (agents must describe unpermitted space honestly, but "in-law suite" is not a permit). RexMont pulls all three during the inspection period.
Can I rent the ADU out in Seattle?: A permitted ADU can be rented long-term under the city's rental rules; short-term rentals are regulated separately, so confirm the current code before you count on nightly income. Many Seattle buyers use the ADU for family first, rent it later, or house-hack from day one.
How much more does a house with an ADU sell for in Seattle?: The twelve-month closings on this page are the answer for Seattle: compare the median here with the city median on the housing-market page. A permitted, separately metered unit with its own entrance commands the most; a basement with a hot plate does not. RexMont prices the two parts separately when we list one.

Buying

Talk to a Seattle home with an ADU specialist before you tour.

Tell us the budget and the sub-market, and whether you are buying only or selling first. A RexMont agent who works this niche sets the call, with the current listings and the twelve-month closings already pulled.

Talk to a home with an ADU specialist

Budget, timing, the area you want. We set the call.

Keep going

Sell a rental property in Seattle
Tenants in place, leases, and timing the sale of an income property.
Property management
RexMont manages ADUs and rentals across Seattle and the Eastside.
Seattle housing market
The city-wide numbers to compare this niche against.
Homes for sale in Seattle
Every active NWMLS listing in Seattle, refreshed hourly.
Seattle neighborhoods
Live inventory and twelve-month sales for every Seattle community.