Backyard cottages are a great addition to our city, providing low hanging fruit for increasing urban density while also providing opportunities for families. Proposed changes to the rules governing backyard cottages are being studied by the City of Seattle and you get to have a say on their implementation through the Environmental Impact Statement (EIS) process.

To comment:

• city council online comment form

• email us at ADUEIS@seattle.gov

• write to Aly Pennucci, City Council Central Staff, PO Box 34025, Seattle, WA 98124-4025

BCBEB (back yard cottage blog editorial board) ADU EIS cheat sheet guide to the EIS comparison of alternatives.

1. Number of ADU's on a lot: Alternative 1 no action keep one per lot.  DADU's  built under current land-use have an impact to the built environment but one generally in keeping with current development patterns in SFR zones.  Allowing three units especially in combination with the removal of the owner occupancy requirement will lead to SFRs designed and built to be rentals with a much higher combined value. Because the combined rentals will have a higher value than one smaller SFR there will be financial incentive to increase the demolition of naturally occurring affordable SFR housing. In addition, the higher combined value of three units will make their purchase that much less obtainable for a family and more appealing for an out of area investor. It has been well documented in the HALA literature that opportunity gaps exist based on proximity and home ownership.  Ownership is one of the primary means of accumulating and maintaining household wealth. This is true for marginalized communities but also for middle class families. Allowing more than one ADU per lot, and eliminating the owner occupancy requirement, will reduce the amount of affordable housing available to families to own.  

Additional alternatives: Portland and Vancouver give special consideration to alley and corner lots. Vancouver only allows DADU's on lots with alleys. These lots can more readily handle increased development with less impact to the urban fabric. The code should be amended to allow these lots to be segregated to create more small scale SFRs that can be sold independently. 

2. Parking: Alternative 2 Remove parking requirement for ADU's. Not a politically palatable but removing the parking requirement will likely not have an environmental impact and will free up yard space for vegetation.

3. Owner Occupancy: Alternative 1- the current proposal to sunset owner occupancy after a period of time is good and should minimize the destruction of naturally occurring affordable housing by speculative developers.  The period of time should be 3 years. Owner occupancy should be required for all properties used short term rentals.  

4. Reduce minimum lot size: Alternative 2 - we already design many cottages on lots less than 4,000 sq. ft in size and the size of the cottage on smaller lots is driven by lot coverage as it should be. 

Additional alternatives: Portland and Vancouver give special consideration to alley lots and corner lots. These lots can more readily handle increased development without disrupting the neighborhood fabric.

5. Increasing the allowable cottage size from 800 to 1,000 sq ft.: Alternative 1 - increasing the allowable size 200 sq. ft. is a great idea and makes it easier to fit in two bedrooms.  However, Alternative 2 excludes the garage and other storage from this calculation potentially allowing 2,000 sq. ft. ADUs.  We frequently design cottages where the garage space is not intended for parking but as part of the cottage.  The city can't and shouldn't mandate that garages are used for parking but not including this space in the allowable square footage will unnecessarily increase the allowable size and bulk of DADUs. And will have a negative impact on the character of neighborhoods, the amount of natural light and vegetation available.  For the large increase in allowable square footage of Alternative 2 to be considered a corresponding reduction in allowable floor area ratio (FAR) should adopted capping the combined size of the two units. This would allow two smaller more equal sized units to be built.

Additional comment: In general the city needs to be more consistent on determining what is included in the allowable gross square footage. Seattle land use code includes all storage areas to the extent that some reviewers for SDCI want to include covered unenclosed exterior space.  The current land use code could be tweaked and specificity added to allow more usable storage area.

Additional Alternative: Consider going to a combination of floor area ratio (FAR) and lot coverage restriction to encourage the creation of two more equally sized family friendly units. 


6. Additional Height: Alternative 1 - while almost all of the cottages we design are built to the allowable height limit the current height limit is adequate for a two story structure.  Additional height can reduce the amount of sunlight reaching neighbors yards.  The multi-family code has provisions that allow additional height with a consideration for the impact of shading on neighboring properties.  Something similar can and should be adopted for DADUs.


7. Lot coverage Limit: Maintain.  Yards do have a value both for families raising children and as green spaces and as a way to reduce stormwater runoff. 

In the world in which we live, small children have almost no opportunity for unsupervised outdoor play.  Urban parks that require that children be constantly monitored by a caregiver cannot fill the void. Back yards provide a safe place for children to play, create, and be outside.  The alternative is often additional screen time with the corresponding negative health effects.

Increasing lot coverage will decrease green space and tree canopy available for habitat for wildlife.  Interconnected vegetated corridors can provide valuable habitat for pollinators and other wildlife even within an urban environment. 

Increasing lot coverage will increase stormwater runoff. As we witnessed, when the west point waste treatment plant went down, we are at capacity for dealing with urban stormwater runoff. The best alternative is to allow stormwater to enter the ground where it can be filtered and recharge streams and lakes.  The rainwise program recognizes the value of groundwater infiltration but also importantly that it is less expensive to provide point source treatment than to create new treatment capacity.  While it is true that the new stormwater code does require increased on site stormwater management, most backyard cottages are below the size threshold to trigger these requirements.


8. Rear yard coverage: Alternative 2 Recognizing that yards do have a value both for families raising children and as green spaces and as a way to reduce stormwater runoff. 


9. Location of entry: Alternative 2. Allow entries 5 ft from nearest lot line with written consent of the neighbor. 

Additional Alternative: Allow the use of side yard easements and or the ability of zero lot line development for DADUs.  This will make it easier to build cottages and allow for a more efficient use of limited yard space.

10. Rooftop features: Alternative 2 -allowing rooftop features, namely shed dormers to extend above the base ("eave height") will not increase the bulk of DADUs allowed under the current land use code and therefore have no negative environmental impact. 

11. Household Size: See comment for number 1.

12. Mandatory Affordable Housing (MHA):  Mandatory Housing Affordability (MHA) does not apply to creation of ADUs in Single Family zones.   

13. Maintain. Property owners renting one or more units, including in Single Family zones, must register for inspections to ensure housing is safe and meets basic maintenance requirements.