Accessory Dwelling Units in Seattle: The Need to Know
By Sean Creamer on August 04, 2023
Folks buying a home in Seattle have likely come across the term "accessory dwelling units."
Sometimes called ADUs, these living spaces allow homebuyers to designate a specific part of their single-family home for use by a family member or a renter. From attached accessory dwelling units (AADU) to detached accessory dwelling units (DADU), each has the potential to generate passive income.
But there are rules and regulations homeowners in Seattle must follow if they want an accessory dwelling unit. That is why the team at Prevu Real Estate put together a quick guide for homebuyers considering a property with an ADU.
What is an ADU in Seattle?
Secondary dwellings come in all shapes and sizes, but there are distinctions between attached accessory dwelling units (AADU) and detached accessory dwelling units (DADU).
An AADU must have a living room, sleeping space, kitchen, bathroom facility, and a lockable entrance door, all within the same principal or primary dwelling unit. An example could be an in-law apartment in a dormer above the home or a finished basement.
A DADU sits on the same plot as the home, with separate utility hookups and a locked entrance. A small guest house, carriage house, or space built above a garage are examples of detached accessory dwelling units.
Where can you have an ADU in Seattle?
The Emerald City has a few zoning areas that allow homeowners in urban and single-family zoned areas to create or repurpose space for an ADU. In 2019, the Mayor of Seattle removed regulatory barriers around zoning, making it easier for property owners to convert space to ADUs in many of the Neighborhood Residential (NR) Zones across the city.
Depending on the size of your lot, you will have an NR1, NR2, or NR3 designation, all of which can have up to two ADUs on the property. One can be an AADU, while the other can be a DADU.
Next up are Residential Small Lots (RSL), which allow for a single ADU on the property. Lastly, Seattle's Lowrise Multi-family (LR) zones allow for an AADU within the multi-family unit.
How much square footage can an ADU have?
The location of your home dictates the size of your secondary dwelling space in Seattle.
DADUs associated with homes with an NR or RSL designation and a minimum lot size of 3,200 square feet on the plot can reach up to 1,000 square feet. If your home sits on an RSL plot, you can have an ADU or DADU that takes up 1,000 square feet. Yet, if you live in an LR zone, your ADU may be limited to a maximum of 650 square feet.
If you want to build a detached unit, the Seattle city planners have several pre-approved designs espousing green building techniques. Through the Seattle ADUniverse portal, you can browse the designs and even get in touch with developers who can help you get started on construction.
Designs for backyard cottages follow green building standards If you are converting space for an attached accessory dwelling unit, you must keep it to 1,000 square feet or under in NR and RSL areas.
Like DADU rules, an AADU in a low-rise zone must be 650 square feet or less.
PREVU SMART TIP
Did you know you can get a rebate from your broker in Seattle? Buying with Prevu you’ll pocket a buyer's rebate up to 1% of your home's purchase price. On a $1,500,000 property, you’d receive up to $15,000 cash back.
What permits do you need for an ADU?
Even if you already have a finished basement ready for a renter, you can't just put out an ad with a room to rent.
Homeowners with space for an ADU must go through an application process, which can take two to six weeks to get approved. The first order of business is ensuring established use through construction permits.
Suppose you already have an in-law unit in the home or a finished basement with a separate, lockable entrance. In that case, all you need to legalize an existing space is a construction permit to establish use.
If you are building an AADU or DADU, you will need a construction addition or alteration permit. From there, you must follow building protocols set by the city, submit the necessary declaration forms, and show a site plan with existing structures and proposals for where an AADU or DADU will be on the property.
What can you use ADUs for?
Some folks have in-laws living with them and need space for them, while others have friends and family visiting from out of town and want to keep them close to home.
But one of the biggest reasons people get a home with an ADU in Seattle is l passive income potential. Considering how many people are moving to Seattle, there is a need for rental units, and an ADU is perfect for housing a long-term tenant. Yet one of the best ways to make money through your ADU is via short-term rentals (STR).
VRBO, Airbnb, and other home-rental services make it easy for folks to find a short-term listing for work or play. The city of Seattle recognizes this and allows homeowners to use an AADU or DADU for STRs, so long as residents register their space.
Homeowners must get a Short-term Rental Operator license, valid for 12 months. Just know that if you plan to launch a short-term rental in Seattle, you need the regulatory license and a business license tax certificate; you could face severe fines and other penalties if you try to operate under the radar.
