Accessory Dwelling Units

A new option for expanding your living space and income

You love your home and your great Seattle neighborhood– but you need more room.

Building an attached accessory dwelling unit (AADU) or detached accessory dwelling unit (DADU) is one of the best ways you can enable visitors, college-aged kids, or elderly relatives to live in close proximity, while at the same time giving them independence and privacy. You can also rent out your new space and enjoy the passive income.

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Many Seattle homeowners are taking advantage of new housing rules by building an AADU or DADU on their property. The City of Seattle has approved legislation that makes it much easier for many homeowners to build an attached or detached accessory dwelling unit. These new rules, designed to increase density and improve the availability of affordable housing, have opened up a new world of possibilities.

An AADU is a self-contained room or suite attached to your home, often in the form of a basement or an added story. Sometimes called mother-in-law suites, these units usually have their own bathroom, kitchen, and private entrance. A DADU, or backyard cottage, is detached from the main house and stands apart in your lawn or garden.

Explore AADUs and DADUs…

Accessory Dwelling Units Showcase

Explore Accessory Dwelling Units

West Seattle DADU

Greenwood DADU

Ravenna Addition and Basement Remodel

Queen Anne Basement ADU Remodel

Northwest Seattle DADU

Magnolia Basement ADU Remodel

Broadview Basement ADU

Backyard Cottage

A modern DADU offers all of the creature comforts of home, but with the added benefits of seclusion, privacy, and a garden view. The average DADU ranges in size from 800 to 1,000 square feet and can be built with a kitchen, bathroom, and even a washing machine.

Mother-in-Law Suites

A mother-in-law suite can help alleviate the crowded, multigenerational living situation that occurs when grandma, grandpa, or an older child moves into the home. Make them feel welcome by creating a fully functional living area complete with a kitchen, bathroom, bedroom, and even a private entrance. This allows keeps them close to the family while allowing them to retain their independence.

Generate Income

Adding a DADU or AADU to your property can generate extra income whether you rent it out long-term or put it on Airbnb for a short-term lease. Depending on what Seattle neighborhood you live in, you could realize your return on investment much sooner thank you think. Talk to our DADU experts to explore the ROI.

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We’ll guide you through the whole process.
We offer virtual consultations to discuss home visits, preconstruction planning, and design.

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AADU and DADU FAQs

How can I find out if I can build an AADU or DADU on my property?

Harjo Construction will come out to your home and provide you with a feasibility study and preliminary design for backyard cottages and basement units. You can contact us here.

How much does a basement AADU cost?

The average cost of a Seattle basement AADU ranges from $175,000 to $275,000. The costs could increase based on design and material choices.

How much does it cost to build a DADU?

The average cost of a Seattle DADU ranges from $250,000 to $550,000. The price could increase based on design and material choices.

How long does the permitting process take?

The permitting process for a Seattle AADU or DADU can take anywhere from four to six months.

How long does a basement AADU take to build?

It can take anywhere from four to six months to complete your AADU or DADU. Several factors can contribute to that, such as weather and unique material availability.

What is the maximum square footage of a DADU?

It can take anywhere from four to six months to complete your AADU or DADU. Several factors can contribute to that, such as weather and unique material availability.

What is the minimum lot size for a DADU?

You need at least 3,200 square feet of lot size to add a DADU to your property.

Do I need to provide off-street parking for an AADU or DADU?

No, but you cannot remove any existing required off-street parking spaces (unless you replace them on your lot).

Do I need to live on the property?

The City of Seattle has removed the owner-occupancy requirement. As such, many homeowners are building AADUs and DADUs for rental income opportunities.

Should I dig out my basement for an AADU?

It depends on several factors, as the cost of digging out a basement could cost more than building a second-floor addition. We will need to come out to your home, walk your property, and learn more about your project before we can provide our expert opinion.

Can I build two AADU’s on my property?

In SF5000, SF7200, and SF9600 zones, you may have either two AADUs or one AADU and one DADU. See additional criteria.

Is building an AADU worth it?

Generally speaking, yes, it is well worth it to invest in building an AADU or DADU on your Seattle property. If you’d like to learn more, give us a call, and we’ll come out to your home and help you determine if building an AADU or DADU makes good sense.

Finding A Contractor for Your Accessory Dwelling Unit in Seattle

With over ten years of experience and countless satisfied Seattle Homeowners, Harjo Construction has the expertise and professional know-how to help you design and build the perfect AADU or DADU.
Although we routinely work on architects’ or designers’ projects, we also have an in-house designer for simpler projects. We can also partner with architects for all magnitude of residential projects.
If you’re ready to speak to someone about your project or have any questions about adding an addition to your Seattle home, contact us or give us a call at: (206) 909-6312.

Let’s get started

We’ll guide you through the whole process.
We offer virtual consultations to discuss home visits, preconstruction planning, and design.

Tell Us About Your Project