Detached ADU
Built under Issaquah's DADU permit. Qualifying projects outside geologically hazardous areas can use the self-certified route.
AIM Builders / ADU construction / Issaquah
ADU Builder in Issaquah, WA
Issaquah allows two ADUs on a lot with a single-family home, in any mix of attached, detached or internal units. We plan Issaquah ADUs around the lot first, because the city's own rules treat geologically hazardous sites differently. You get a written, itemized estimate before construction starts.
Planning sketchStart with a plan
Make room for what comes next.
- Detached, attached, or a garage conversion?
- What's the intended use: rental, family, or a home office/studio?
ADU rules in Issaquah
What Issaquah allows.
The city's ADU FAQ is direct about the basics. A lot with an existing single-family home may add two ADUs in any configuration of attached, detached or internal. Each ADU may not exceed 1,000 square feet, unless a basement is converted without any interior or exterior expansion. Homeowners are not required to live on site, and an ADU can be sold and owned separately from the main home.
ADUs still have to meet all applicable zoning standards. One exception helps on some lots: if the lot abuts an alley, the ADU does not have to meet the rear yard setback. The city does not offer pre-approved ADU plans, so each unit is drawn for its site.
Applications go through MyBuildingPermit.com, and Issaquah does not accept paper applications or plans. The ADU submittal list includes a utility service application, a water meter sizing form and a tree protection fence detail. Where they apply, it adds a fire flow and water availability worksheet and a King County sewer use certification.
Rules checked against the sources listed below on October 26, 2026. Codes change, so we confirm the current requirements for your address before design.
Lot and site
Slopes, soils and the DADU route.
A new backyard unit uses Issaquah's Detached ADU permit. The city also runs a self-certified DADU program that streamlines review for qualifying projects. Projects in geologically hazardous areas do not qualify, so a lot in one of those areas goes through standard review. Issaquah publishes soils report requirements for both the ADU and DADU permits.
That makes the early site visit count. Before anything is drawn, we look at grade, access for equipment, the trees that need protection during work and the route to water and sewer service.
ADU types in Issaquah
About our ADU construction Four ways to add a unit.
How it starts
From the first walk to a written estimate.
A consultation with Adi
Adi personally takes every in-home consultation. You talk through what you want to change, what matters daily and what you hope the home could do.
A walkthrough of your space
We measure, check structure and access, and look at the rooms as they are today, so the plan fits the house you actually have.
A written, itemized estimate and schedule
You see exactly what you are paying for, with the scope and schedule in writing before any demo starts.
Issaquah ADU questions
Questions we hear in Issaquah.
How many ADUs can I add in Issaquah?
Two. Issaquah's FAQ says a lot with an existing single-family home may add two ADUs in any configuration of attached, detached or internal.
How big can an Issaquah ADU be?
Up to 1,000 square feet. The exception is a basement converted into an ADU without any interior or exterior expansion.
Do I have to live on site to rent or sell an Issaquah ADU?
No. The city says homeowners are not required to live on site, and an ADU can be sold and owned separately from the primary home.
What is Issaquah's self-certified DADU program?
A streamlined path for detached ADU permits on qualifying projects. Projects in geologically hazardous areas do not qualify. Applicants apply through MyBuildingPermit.com and upload the city's Affidavit of Self-Certification.
Does Issaquah offer pre-approved ADU plans?
No. The city does not offer pre-approved ADU plans, so each ADU is designed for its own lot.
What will an ADU cost in Issaquah?
Each project gets a written, itemized estimate after a site visit. Slope, soils, access and the run to water and sewer move the number most, so we do not quote before walking the lot.
Step 1 of 2Your project
Request a free ADU consultation in Issaquah
Let’s plan your adu or garage conversion.
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Roof repair is available only as part of a larger remodeling scope.
Planning an ADU in Issaquah?
Talk it through first.
Share your address and what the unit is for. Adi personally takes every in-home consultation, and the walkthrough covers the lot, access and utilities before any design or price.
Call (425) 671-2917Keep planning
ADU pages for nearby cities.
Each page covers that city's own ADU rules and permit process.
Free In-Home Consultation
Let’s look at your lot in Issaquah.
Tell us what you would like to change. Adi visits, measures and listens, and you receive a written, itemized estimate with one point of contact from the first walkthrough to the final details.
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