All ADU Regulations

Issaquah, Washington

Issaquah is a perfect place to build an ADU. Here are Issaquah's up-to-date ADU rules.

July 21, 2023
Get Started  


Issaquah is a quaint town located on the southern area of Lake Sammamish, 17 miles southeast of Seattle. Surrounded by greenery and mountains, the town offers a blend of hiking trails, outdoor activities, and scenery of three distinct peaks - Tiger Mountain, Cougar Mountain, and Squak Mountain. The town is a picturesque city that presents a blend of natural beauty and modern amenities.


Accessory Dwelling Unit (ADU) projects must meet all of Issaquah’s Zoning Code requirements, specifically Chapter 18.500.090. A property's zone is available on the Issaquah Zoning Map or within the City's document center.

Number of units

Only one ADU is permitted for one single-family detached or ADU on its own legal lot.

Building size

The maximum size of an ADU must either be 1,000 square feet, encompass a full floor; or encompass up to 125% of the garage, if over the garage.


A 4’ wide walkway shall be constructed from the address side of the right of way or driveway to the ADU primary entrance. Minimum walkway requirements (4’) will not be counted against the site’s maximum impervious surface calculation.


One parking space is required for an ADU on a single-family lot.


An owner of the property must occupy either the primary residence or the Accessory Dwelling Unit for more than six months of each calendar year.

Cottage is here to help you navigate the ADU process. Reach out to us and we’ll help you build a custom ADU to fit your unique property characteristics and local regulations!

Design and build with confidence.