ADU guide · Eastside Washington
Can I Build an ADU? The Eastside Guide, City by City
Backyard cottage. In law suite. Granny flat. Mother in law unit. Guest house. Washington calls all of these accessory dwelling units, or ADUs. This guide tells you, in plain English, whether you can build one where you live.
The short answer
Yes. Washington law requires cities to allow two ADUs on most lots zoned for a single family home. Your city sets the size, setbacks and fees.
Source: Washington Department of Commerce, ADU guidance and RCW 36.70A.681, the state ADU law passed as House Bill 1337.
Step one
Find Your City
Each city guide follows the same five parts: the short answer, the confirmed rules, what can complicate your project, a realistic timeline, and how to check your own lot. Every number links to the city code it came from.
Bellevue
Yes. Every Bellevue lot zoned for a single family home qualifies for up to two ADUs, each up to 1,200 square feet.
Read the Bellevue guide →Bothell
Yes. Every lot inside Bothell city limits that is zoned for homes qualifies for up to two ADUs, each up to 1,200 square feet.
Read the Bothell guide →Edmonds
Yes. Most Edmonds lots in the LDR-L zone qualify for up to two ADUs, each up to 1,200 square feet.
Read the Edmonds guide →Issaquah
Yes. Every lot inside Issaquah city limits that is zoned for homes qualifies for up to two ADUs, each up to 1,000 square feet.
Read the Issaquah guide →Kenmore
Yes. Kenmore allows up to two ADUs on any lot where a single family home is allowed.
Read the Kenmore guide →Kirkland
Yes. Any Kirkland lot zoned for a single family home qualifies for a detached ADU up to 1,200 square feet, and you do not have to live on the property.
Read the Kirkland guide →Redmond
Yes. Every lot inside Redmond city limits that is zoned for homes qualifies for up to two ADUs, each up to 1,000 square feet.
Read the Redmond guide →Sammamish
Yes. Every lot inside Sammamish city limits with a single family home qualifies for up to two ADUs, each up to 1,000 square feet.
Read the Sammamish guide →More cities are on the way: Woodinville, Mercer Island, Shoreline, Newcastle, Lynnwood, Mountlake Terrace, and unincorporated King and Snohomish counties. Your city not here yet? The call at the bottom of this page covers every Eastside city.
Side by side
Same State Law, Different Backyards
Every city follows the same state floor. The details on top of it are where lots win or lose. A detached ADU in Redmond can sit 3 feet from the side property line. In Bellevue it needs 5. In Edmonds it needs 10. On a narrow lot, that gap decides whether a cottage fits at all.
One rule is the same everywhere in this guide: you do not have to live on the property.
| City | ADUs per lot | Size of each | Height, detached | Side setback, detached | Parking | City impact fees |
|---|---|---|---|---|---|---|
| Bellevue | Up to 2 | 1,200 sq ft | 24 ft | 5 ft | None under 1,000 sq ft | $4,092 |
| Bothell | Up to 2, or 1 near critical areas | 1,200 sq ft | 30 ft | 5 ft | None | About $3,300 plus fire and parks |
| Edmonds | Up to 2 | 1,200 sq ft | 24 ft | 10 ft | None for the first | $4,306.83 |
| Issaquah | Up to 2 | 1,000 sq ft | 25 to 30 ft | Same as house | None | None |
| Kenmore | Up to 2 | 1,000 to 1,500 sq ft | 35 ft | Same as house | None | None |
| Kirkland | Confirm with city | 1,200 sq ft | 15 ft near rear line | 5 ft | One, or none near transit | None up to 800 sq ft |
| Redmond | Up to 2 | 1,000 sq ft | 38 ft in NR zone | 3 ft | None | $5,757 listed |
| Sammamish | Up to 2 | 1,000 sq ft | 24 ft | 5 ft | None with 4 spaces | About $10,570 |
A setback is the minimum distance between a building and your property line. An impact fee is a one time charge that helps the city pay for roads, parks and growth. These are headline numbers for a typical lot. Fees are 2026 city impact fees for one ADU. Each city guide explains the exceptions and links every number to its source.
Questions every city shares
Before You Pick a City Guide
What is an ADU?
An ADU is a second, smaller home on the same lot as a house, with its own kitchen, bathroom and place to sleep. It can be attached to the house, like a basement or garage conversion, or stand on its own in the backyard. Backyard cottages, in law suites, granny flats, mother in law units and guest houses are all ADUs.
Do I need to hire an architect?
No, not by law. Washington state does not require a licensed architect for homes with one to four units, and an ADU falls under that rule (RCW 18.08.410). The city still needs complete plans, and some work, like a geotechnical report or certain structural designs, needs a licensed engineer.
Do I have to live on the property?
Usually no. Washington law stops cities from requiring the owner to live on site. The one exception is a city that chooses to limit short term rentals, which can then require it. None of the eight cities in this guide requires it.
Why are the rules different in every city?
State law sets the floor. It says cities must allow two ADUs and cannot cap their size below 1,000 square feet (RCW 36.70A.681). Each city writes the rest: setbacks, height, parking, fees, and what triggers extra review, like steep slopes or big trees. That is why a lot that works in one city can fail in the next one over.
Which city has the lowest fees?
Among the cities in this guide, Issaquah and Kenmore charge no city impact fees on ADUs, and Kenmore waives the building permit fee too. Kirkland charges none on ADUs of 800 square feet or smaller. Sammamish runs highest, at about $10,570 for a 1,000 square foot ADU. Fees change every year, so confirm with your city before you budget.
Your lot
Talk to the Builder
This guide tells you what your city allows. Your lot is one of a kind. A short call confirms what fits on yours.
Check if my property qualifiesUpdated October 28, 2026. City rules change. Each city guide shows the date its rules were last checked. This page is general information, not a permit decision.