Auxiliary Dwelling Units: ADU vs. DADU

Auxiliary Dwelling Units: ADU vs. DADU

Auxiliary Dwelling Units are referred to as many things: backyard cottage, in-law apartment, granny flat, you name it. The various names are related to the fact that an ADU can take on many forms. Whether you’re looking for a garage conversion, basement living space, addition or detached unit, this small footprint space can make a huge impact.



Image Credit: City of Newberg, OR Community Development Department

An ADU (Auxiliary or Accessory Dwelling Units) is a self-contained living space within an existing single-family dwelling. These typically including their own kitchen, bathroom, and separate entrance. Though attached to the existing home, ADU’s allow you to maintain privacy and square footage, while creating a separate living space.

DADU’s (Detached Auxiliary Dwelling Units) are the same, simply detached from the property’s main house. In the City of Seattle, ADU’s are limited to 1,000 square feet in a single-family zone and 650 square feet in a low-rise zone. If you are curious about the requirements, check out your local building departments website or give us a call, chances are we will know what the requirements are for your location.

Finding the right type of ADU for your property takes extensive research and planning. From city zoning codes and building setbacks to site feasibility, there is a lot to explore in the planning process. Engaging with a vetted, experienced, professional General Contractor is vital to assure that the smallest details have been accounted for.

Small Space, Big Benefits


Ballard Guest Cottage, Build by Better Builders

Building an ADU or a DADU has quickly become a popular option for Seattle area homeowners. In an effort to improve housing accessibility, the City of Seattle passed legislation making it easier to build auxiliary housing. With economic opportunity growing here in Rain City, we continue seeing an influx of residents. So we must keep finding new ways to increase our housing to keep pace. One of the reasons that these spaces have become so popular is because for a small space, you can see relatively large return depending on your use case.

  • Auxiliary Units, attached or detached, can help promote economic and social diversity in neighborhoods that may otherwise be out of reach for the average renter.
  • ADU’s and DADU’s can provide valuable rental income for the homeowner. With options ranging from full-time renting to Airbnb style, this can be a great way to get a little extra cash in your pocket. Additionally, it will likely increase your overall potential property resale value.
  • For those with older family members who may need assistance, this can provide alternative to expensive assisted living facilities. The same goes for providing low cost housing for adult children who may need to return home for a while. Whatever the case, having separate, private spaces is incredibly valuable.
  • Recently we have been seeing many people utilizing their ADU space to create a separate workspace. Whether you’re running a home business or are fighting through indefinite Covid-19 induced work from home status, it’s worth considering! Being to separate being at work from being at home is invaluable. Create a more professional environment and eliminate the commute by creating the ultimate work-from-home “office”.
Marin Ryles

About Marin Ryles

With an educational background in Marketing and Communications, Marin loves to write and find new ways to connect with our clients and followers.