What is an ADU?

An Accessory Dwelling Unit (ADU) is a smaller, independent home located on the same property as a primary residence. It has its own kitchen, bathroom, and living space. ADUs go by many names—cottage, in-law suite, backyard home—but they all provide extra space and new possibilities.

There are two main types of ADUs:

Detached ADUs (DADUs)

A separate building like a backyard cottage, tiny house, or converted garage that doesn’t share any walls with the main home. Great for renters, extended family, or extra privacy. Want to see what they look like? Browse our gallery of pre-approved plans.

Attached ADUs (AADUs)

A unit that’s built into or onto the main house like a finished basement, over-garage apartment, or side addition. Ideal when space is tight or the lot has building limitations.

ADU Toolkit Home

Return to the ADU Toolkit landing page.

Why Build an ADU?

Explore the personal, financial, and community benefits of ADUs.

Explore Kirkland’s Pre-Approved Plans

Save Time. Save Money. Start Building Sooner.

Planning Your ADU

From Idea to Reality—Here’s How to Get Started

Paying for Your ADU

An ADU is a serious investment—but it’s also one that can pay off over time through rental income, selling the unit, increased property value, or family support. Let’s talk cost, financing, and how to plan ahead.

ADU Permitting Process

Step-by-Step Guidance to Get Your Project Approved

Moving In or Renting Out

What Happens After Your ADU Is Built

Why the City Supports ADUs

Building a More Inclusive, Affordable, and Sustainable Kirkland

Common ADU Questions

Answers to some of the most common ADU questions.

ADU Regulations

Regulations related to building ADUs in Kirkland.

Building and Fire Code Scenarios

Scenarios of how ADUs will be evaluated based on the Kirkland fire and building codes.

Building an In-Law Unit? How to Save Time and Money on an ADU

This content is to share the benefits of using one of the City's pre-approved ADU plans.