HomeWork: If you've ever wished you had a way to earn some rental income with your home or simply had more space, a backyard cottage might be a dream worth exploring.

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Q: What is a backyard cottage, and why would I want to build one?

A: Imagine having a private getaway or guest house tucked neatly into your own backyard. Since 2009, when the city started permitting this new type of development, hundreds of Seattle homeowners have chosen to invest in their very own backyard cottage retreat.

If you’ve ever wished you had a way to earn some rental income with your home or simply had more space, a backyard cottage might be a dream worth exploring. However, the regulations can be a bit confusing, and Seattle is in the process of changing them.

First off, what is a backyard cottage? Detached accessory dwelling units, or DADUs, as the city of Seattle calls them, are small, standalone houses built behind your main home. They allow you to maintain your privacy and all the square footage in your main house, while creating extra living space. Some homeowners opt to build them over a new or existing garage.

Backyard cottages provide many of the benefits of single-family homes, with no shared walls and a lower-density-neighborhood lifestyle. They also promote economic diversity in neighborhoods that might be out of range for average-income renters.

Backyard cottages can provide passive rental income for the homeowner. Some are renting right now for around $1,200 to $2,000 per month, or up to $24,000 per year. As a vacation rental, a cottage could earn you even more. This can help homeowners of modest means stay in their homes or simply put extra cash in your pocket to pay the mortgage or for home improvements.

An often-overlooked benefit is that backyard cottages can help reduce sprawl by slowly increasing density while taking advantage of existing infrastructure. When compared to high-rise developments, backyard cottages help preserve the character of our beloved Seattle neighborhoods.

If you are thinking about building a backyard cottage, the first step is to make sure you know all the rules. In Seattle, for example, there are some major changes in the works. Let’s look at the current regulations.

  • Your lot must be 4,000 square feet in a single-family zone.
  • Only 800 square feet is allowed for cottages in single-family zones.
  • Like any construction project, your cottage must meet current land-use and building standards. No surprise there.
  • You must create one off-street parking space for your new backyard cottage.

As of 2017, only 579 backyard cottages have been built in Seattle out of approximately 75,000 potentially eligible lots. To put that into perspective, Portland already had 720 in 2016. To encourage more to be built, the Seattle City Council is considering changing the regulations, such as increasing the maximum square footage of cottages and removing the off-street parking requirement. The council is currently pursuing an environmental impact statement.

If your plans for a backyard structure do not include a sleeping area, there are some permitting alternatives you may be able to consider. For standalone backyard structures under 750 square feet, you might be able to qualify for a subject-to-field-inspection permit, which saves time and money. Examples of detached accessory structures might be art studios, workspaces, retreat spaces or storage areas.

For even smaller structures, like garden or storage sheds, whose roof area footprint is less than 120 square feet, you probably won’t need a permit at all. It’s always wise to confirm with local officials before you begin any construction project.

If you are considering investing in a backyard cottage, the first step is to reach out to a qualified design-build firm or architect to discuss your eligibility. For full-service custom construction, expect to pay between $250 and $350 per square foot.


Denny Conner is the president of CRD Design Build and a member of the Master Builders Association of King and Snohomish Counties (MBAKS), and HomeWork is the group’s weekly column. If you have a home improvement, remodeling or residential homebuilding question you’d like answered by one of the MBAKS’s more than 2,800 members, write to homework@mbaks.com.