Cities call them accessory dwelling units. Most of us know them by other names-including cottages and mother-in-law units. Whatever name you might know them by, these living spaces typically include their own living space, kitchenette, and bathroom, and either share a wall with the main house or are detached, usually situated in a backyard. And they are growing in popularity as municipalities are increasingly seeing them as a way to answer a variety of issues. Some of their benefits, according to the Municipal Research and Services Center of Washington include:


ADU's increase the supply of affordable housing
Satisfy a growing need for smaller housing
Make efficient use of existing housing stocks and infrastructure
Provide homeowners with extra income
Make it possible for adult children to provide care and support to a parent in a semi-independent living arrangement
Can help first-time buyers qualify for loans and help offset mortgage payments

Many municipalities in the South Sound currently allow attached ADU's, detached ADU's, or both. Tacoma allows attached ADU's in almost all of their zoning areas, and detached ADU's in some of their residential zones, while unincorporated Pierce County allows both attached and detached ADU's in nearly the entire county.

SustainaBuild recently built our first detached Accessory Dwelling Unit, although that wasn't the initial plan. The Homeowner needed additional storage so the plan was to build a 200 sq. ft. durable, attractive shed with a covered porch area for barbecuing, using reclaimed materials where we could, including windows, door, cedar siding. But as the plan progressed and the level of customization increased, including adding a loft area accessed by a customized rolling ladder, she decided at the completion of the project that she would rent out the cottage or possibly move-in herself. So we installed some reclaimed bamboo flooring, an EPA-rated wood stove, and for a little more than the cost of a shed, she has a detached 200 sq. ft. cottage. However, she is still left with her original dilemma of where to store her stuff, so we are now designing a real shed- an addition to her new cottage complete with storage space, a mini-refrigerator, and a composting toilet.