"We hired MNBE to build our ADU in Bellevue, and the entire experience was amazing. They handled everything from foundations and framing to kitchen, siding, windows and HVAC."
Zena Heywood
Bellevue, WA · Attached ADU
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ADU rules by city
Seattle, the Eastside, the north end and South King County, side by side: how many ADUs, how big, how tall and whether you need parking. Written by MNBE founder Aharon Ben Elisha. Checked October 28, 2026.
15 cities + King & Pierce counties Every rule linked to its code Updated for 2026
One State Law, Local Rules
Same state law, different city rules.
Washington's ADU law, HB 1337, set minimum ADU allowances for cities and counties inside urban growth areas: generally two ADUs on eligible single-family lots, with limits on owner-occupancy, parking and size-cap rules. Statutory exceptions and local site standards still apply, and each city wrote its own code on top of that floor, so the numbers differ from one city line to the next.
The table below puts the headline rules side by side. Each city's guide has the full rules with the code section and official source behind every number. Codes change often; we confirm the current version for your address before design begins.
Common questions answered in depth: how many ADUs fit on a lot, two-story ADUs, ADU addresses and owner occupancy.
Across the Region
The region, by the numbers.
What these cities and counties have in common, and where they differ.
16
Guides
15 cities plus unincorporated King and Pierce counties.
2
ADUs per lot
Allowed on most urban residential lots.
1,000–1,500sq ft
Size caps
From 1,000 sq ft to Kenmore's 1,500 sq ft DADUs.
No
Owner occupancy
Not required anywhere in these guides.
Side by Side
ADU rules, city by city.
Headline rules for the main single-family zones. Open a city's guide for the full rules and sources.
| City | Headline rules | Full guide |
|---|---|---|
| Seattle | Two ADUs in any mix. 1,000 sq ft, or 1,200 with three or more bedrooms. DADU height follows the house, 32 feet in Neighborhood Residential zones. No parking. | Seattle guide → |
| Bellevue | Two ADUs; detached allowed since July 2025. 1,200 sq ft. DADUs 24 feet. No parking under 1,000 sq ft or near major transit, otherwise one space. | Bellevue guide → |
| Kirkland | Two ADUs of either type. 1,200 sq ft. Height follows the house, 25 to 30 feet. No ADU parking since September 2026. | Kirkland guide → |
| Redmond | Two ADUs. 1,000 sq ft. Up to 38 feet in NR. Backyard buildings capped at 60% of the house's ground floor. No parking. | Redmond guide → |
| Shoreline | Two ADUs in any mix. 1,200 sq ft. Height by zone, 23 to 35 feet. No parking minimums. | Shoreline guide → |
| Edmonds | Two ADUs per house. 1,000 to 1,200 sq ft by zone. DADUs 24 feet. No parking for the first ADU, one space for a second. | Edmonds guide → |
| Bothell | Two ADUs (one on lots with critical areas). 1,200 sq ft. DADUs 30 feet. No parking minimums. | Bothell guide → |
| Lynnwood | Two ADUs in any mix. 1,000 sq ft. 35 feet in RN. No parking for units under 1,200 sq ft. | Lynnwood guide → |
| Sammamish | Two ADUs. 1,000 sq ft. DADUs 24 feet. ADUs exempt from floor area and hardscape limits. | Sammamish guide → |
| Mercer Island | Interim rules: two ADUs, 220 to 1,000 sq ft, 30 feet. Parking unless near a major transit stop. Design matches the house. | Mercer Island guide → |
| Medina | Two ADUs per home. 1,000 sq ft. 25 feet. One parking space per ADU. Not on lots with critical areas or in shoreline jurisdiction. | Medina guide → |
| Kenmore | Two ADUs. DADUs up to 17% of the lot, 1,500 sq ft max on lots of 6,000 sq ft or more. 35 feet. No parking. Can be sold separately. | Kenmore guide → |
| Renton | Two ADUs. 1,000 sq ft. DADUs 24 feet. One space per unit unless near major transit. Free permit-ready ADU plans. | Renton guide → |
| Tukwila | Two ADUs. Up to 1,400 sq ft. DADUs 28 feet. No parking. No rentals under 30 days. | Tukwila guide → |
| King County (unincorporated) | Urban lots such as White Center: two ADUs, 1,000 sq ft heated (up to 1,500 by trading unheated space), 35 feet, no parking. Rural lots: generally one ADU. | King County guide → |
| Sumner & Lake Tapps | Sumner: two ADUs, 1,000 sq ft, 24 feet, one space per ADU. Most Lake Tapps lots follow Pierce County: two ADUs in the urban growth area, one in rural areas. | Sumner & Lake Tapps guide → |
Checked October 28, 2026 against each city's code; the sources are listed in each guide. A plain-English summary, not legal advice.
Reviews
What Seattle homeowners say about building with MNBE.
Verified five star reviews from owners we guided through ADU feasibility, permitting, and construction.
"We hired MNBE for a full renovation of our 100 year old home and the results exceeded expectations, structural upgrades, new insulation, a luxury bathroom, a high end kitchen, a new roof and mini split AC."
Dave Gierok
Redmond, WA · DADU
"My mom hired MNBE Construction for her two-bedroom DADU in Seattle, and watching the process up close was impressive. They did it all: design, architectural plans, the building permit, and the full construction. … The communication was excellent and there were never any surprises."
Maryam Z.
White Center, WA · ADU
Schedule Free Estimate
FIVE-STAR RATEDRATED ON GOOGLE
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FAQs · ADU rules by city
Comparing cities.
Short answers from the guides. For your exact lot, call us or book the free site visit.
In Kenmore, a DADU can be 17% of the lot area on lots of 6,000 square feet or more, capped at 1,500 square feet, which takes a lot of about 8,824 square feet. Unincorporated King County allows up to 1,500 square feet of heated space on qualifying urban lots. Tukwila's limit is 1,400 square feet.
Seattle, Kirkland, Redmond, Shoreline, Bothell, Lynnwood, Kenmore, Tukwila and unincorporated King County generally require no ADU parking. Bellevue, Renton, Mercer Island, Medina, Sumner and unincorporated Pierce County may require it, subject to transit exemptions. Edmonds requires none for the first ADU and one space for a second outside transit areas, and Sammamish needs no added space when the lot already has four.
Renton offers free permit-ready ADU plans, Kirkland has pre-approved DADU plans, and Seattle has pre-approved plans with new ones on the way. Lynnwood's program is still being developed.
No. State law prohibits owner-occupancy requirements for ADUs, and none of the cities in these guides require it.
Contact Us · Free Estimate
Tell us about your project.
We'll check your address against your city's ADU code and get back to you within one business day with a clear next step.
Contact information
Thank you for considering MNBE. Thank you for considering MNBE. Tell us your address and we will tell you, in writing, what your city's code allows on your lot. We respond within one business day, Monday through Saturday.
(206) 637 0044
info@mnbe-wa.com
2014 Fairview Ave Unit 2308, Seattle, WA 98121