Accessory Dwelling Units (ADUs)
and cottages--often referred to as mother-in-law apartments or guest houses--are
habitable living areas added to, created within, or detached from single-family
homes that meet the basic living, sleeping, eating, cooking, and sanitation
needs of their residents.
ADUs can be attached,
detached, or inside units. Detached units are located on
the main building's property, but share none of its walls. Such units can be
separate structures, or part of a detached garage or other detached building on
the property. Attached ADUs are configured such that they are a
structural part of the main building. They can be an addition or part of a
remodeled attached garage. Inside ADUs are built somewhere within the
existing main building (e.g. in a basement or upstairs area.)
Though requirements vary with
municipality, a typical ADU ranges in size from 400 to 900 square feet.
Though ADUs have been around
for decades, their popularity has grown in recent years for a number of reasons.
Here are a few:
1. ADUs make great rentals.
They help diffuse mortgage payments, property taxes, and maintenance and repair
costs, and they offer retired homeowners a source of regular income.
2. ADUs are one way to meet
the demand for further, affordable rental housing in desirable neighborhoods
without changing the neighborhoods' character or creating the need for new
infrastructure (roads, sewers, schools, etc.) Plus, ADUs cost 25 to 40 percent
less to build than comparably-sized new units because they do not involve
developing new land and have lower associated construction costs.
3. ADUs offer older kids and
guests (not to mention you the homeowner!) a little breathing room and a home
away from home.
Who Can Build an ADU?
If specific requirements
(zoning and building permits, size and design specifications, etc.) are met, the
following Puget Sound area cities and towns allow the addition of an ADU:
Bellevue, Beaux Arts Village, Bothell, Clyde Hill, Hunts Point, Issaquah, Kirkland, Medina, Mercer Island, Newcastle,
Redmond, Seattle, Woodinville, and
Yarrow Point. Note that not all cities and towns allow all types (detached,
attached, inside) of ADUs.
How Can ABI Help?
If you are interested in or are in the process of adding an ADU to your
residence, ABI would be very happy to provide any or all of the following
● Initial feasibility
● ADU design
● In-progress construction
Feel free to call us at (206)
522-8077, or email us at
firstname.lastname@example.org for further information.
ARCH Housing Website
also provides helpful information for those interested in building an ADU.