Small is the new green

Increasing environmental awareness along with economic and demographic trends favor smaller house sizes. Many cities are doing their part by updating zoning codes to allow cottage housing and small backyard cottages (detached ADU's) on residentially zoned lots. Seattle and Portland are two cities which allow backyard cottages up to 800 sq. ft. in size. These small houses provide opportunities for families, while increasing housing stock density and diversity. Continue reading for more information about small house design and Seattle's backyard cottage ordinance or contact us to find out if your lot is eligible for a backyard cottage.

backyard cottages - regs.

Backyard Cottages - Seattle 

In 2009 the City of Seattle expanded the their demonstration backyard cottage ordinance to allow backyard cottages in all Seattle neighborhoods.  Fast forward to 2016 and the city is poised to expand the ordinance still further.  Follow this blog to lean more about these proposed changes and their implementation. 

To learn more about your Seattle lot click on the following link. 

Enter your address in the upper left hand corner
Zoom in to your lot
Right click on your lot and click the green more link

On the upper left hand corner under under base zone it will say if a detached accessory dwelling unit is allowed.  If so, there are additional requirements that will determine what and where you can build. Send us an email with your address and tell us what you plan to use the cottage for and we can perform a free analysis of your project.


Backyard Cottage Parking 

Backyard cottages (detached ADUs) require one parking space in addition to any other parking space required for the primary residence. These parking spaces can be provided in tandem. However, these spaces cannot be located in the required front setback.

If your site has physical constraints that prevent you from providing the additional parking space an exception to this requirement may be granted.

Can I convert my garage to a backyard cottage (detached ADU)?

For a single family lot in a single family zone in Seattle an existing detached accessory structure may be converted to an accessory dwelling unit (DADU) if it meets certain requirements outlined in the Seattle Municipal Code. One of these requirements is meeting minimum side and rear yard setbacks 5 ft (DADUs are not allowed in required front setbacks). Most detached garages are built on or within 5 ft of the side property line. At the discretion of the director  these to be converted to backyard cottages if the accessory structure was constructed legally prior to June 1, 1999 and the conversion does not increase its non-conformity.

Backyard Cottages - Other Cities 

A number of northwest cities and counties have modified their zoning ordinances to allow detached ADUs. They appeal to families because they provide opportunities to grow or to provide rental income. They appeal to cities because they provide additional housing options and increase density. Contact us for more information about specific cities.

In general the requirements have a few things in common. 

owner occupancy: Seattle and most cities require owner occupancy either the primary structure or the detached ADU. Portland Oregon is a notable exception.

minimum lot size: Detached ADUs are restricted to lots over a specific size. This varies quite a bit as different jurisdictions have different norms. In Seattle, the minimum lot size is 4,000 sq. ft. 

maximum cottage size and height: Detached ADUs are restricted by size and height limitations. Sometimes this is a maximum floor area other times it is a percentage of the size of the primary residence.

permitting process: Cottages are sometimes allowed outright which means that they can be permitted if they meet all of the requirements. Other times they require conditional use permits which may involve public hearings and other steps that are often time consuming and costly.  New ADUs must meet the same building codes applicable to houses.


A short list of Washington cities that allow backyard cottages;
Bremerton, Burien,  Kent, Kirkland, Mercer Island, Mill Creek, Mountlake Terrace, North Bend,  Redmond, Sammamish, Spokane, Seattle, Vancouver.
Unincorporated Areas;

                King County, Pierce County

Other northwest cities;
    Portland Oregon, Vancouver British Columbia.
Other cities considering backyard cottages;
    Bellevue, Denver Colorado, Madison, Wisconsin.