Councilmember O’Brien Unveils Backyard Cottage Proposal

If you were beginning to think backyard cottages were going to end up on the legislative agenda backburner, think again. Councilmember Mike O’Brien has formally unveiled his legislation to remove barriers from building backyard cottages in Seattle. During the review of backyard cottage housing, O’Brien and staff from the Office of Planning and Community Development conducted extensive public outreach to get feedback on issues like requirements for off-street parking, owner occupancy, height limits, and maximum square footage of units.

Known more formally as Detached Accessory Dwelling Units (DADUs), the City has permitted them on a widespread basis since 2010 and has experienced very low interest in development due to regulatory requirements. In total, 221 individual DADUs have been built. The City estimates that some 4,000 DADUs could be built if property owners of just 5% of eligible lots decided to pursue development of these units.

For the wonks out there, Councilmember O’Brien put together a helpful side-by-side comparison of existing code versus proposed regulatory changes:

Summary of Proposed Changes

#	Policy Area	How It Is Today	Proposed Change
1	Attached Accessory Dwelling Unit (ADU) and Detached ADU (DADU) on the same lot	A lot with or proposed for a single-family dwelling may have no more than one accessory dwelling unit.	Allow a property to have both an ADU and DADU within the existing building envelope: Does not change the total size of buildings on a lot and development standards like lot coverage limits, yards, and setbacks would continue to apply; and Does not increase the total number of people who can live on the lot (if unrelated persons occupy any of the units, the total number of persons occupying all units may not altogether exceed eight)
2	Off-street parking requirement	One off-street parking space is required for the accessory dwelling unit, unless located in an urban center or urban village.	Remove requirement for off-street parking: A property owner would still be able to provide an off-street parking space if they have space and believe it is a desirable amenity for prospective tenants; and Removing this requirement will allow some properties who have insufficient space for an additional off-street parking space, to add an ADU or DADU.
3	Owner-occupancy requirement	An owner must occupy either the principal dwelling unit or the accessory dwelling unit.	Require owner-occupancy for 1 year, then requirement expires: Maintains current dynamic of homeowners designing/creating ADU/DADUs; Addresses some homeowners' concerns by preventing landlords and investors from creating ADU/DADUs; Gives flexibility to homeowners to move after 1 year, rent both units Increases homeownership options for prospective homebuyers who can use rental income from ADU/DADU; and Alleviates some of lenders' concern with financing.
4	Minimum lot size for DADUs	The current minimum lot size for a site with a DADU is 4,000 square feet.	Reduce the minimum lot size for a site with a DADU to 3,200 square feet: Approximately 7,300 more lots become eligible to build a DADU; and Development standards like lot coverage limits, yards, and setbacks would continue to apply and would govern the footprint, scale, and location of a DADU.
5	Maximum square footage of a DADU	The maximum gross floor area of a DADU is 800 square feet including any garage and storage areas. The maximum gross floor area of an ADU is 1,000 square feet.	Increase the maximum gross floor area of a DADU to 1,000 square feet; exclude garage and storage areas: Consistent maximum square footage for ADUs and DADUs; Facilitates family-size units; More flexibility for DADUs over garages; and Other development standards would continue to regulate scale of DADUs (lot coverage, height limit, etc.).
6	Rear yard coverage limit	A maximum of 40% of a rear yard may be covered by accessory structures and any portion of the main house. This limit is in addition to the overall lot coverage limit for a single-family lot.	Increase rear yard coverage to 60% for one-story DADUs: More flexibility for one-story designs, which are: less visible than two-story DADUs; better for limited-mobility tenants and aging-in-place; and Does not increase the overall lot coverage limit for a single-family lot
7	Location of entries	DADU entrances cannot face the nearest side or rear lot line unless that lot line abuts an alley or other public right-of-way.	Allow DADU entrances on any façade, provided it is 10 feet from the lot line if located on the façades facing nearest side or rear lot line (unless abutting right-of-way): Adds design flexibility; Addresses challenge we've heard from architects; and Continues to address privacy concerns.
8	Height limit	The maximum height limit depends on the width of the lot; on wider lots, a taller DADU is permitted (see Table A below).	Increase maximum height by 1-2 feet and simplify code (See Table B below): Makes 2-bedroom DADU feasible on more lots; and Facilitates family-size units.
9	Roof features	Exceptions for roof features for a accessory units are not permitted.	Allow exceptions from height limit for projections (e.g., dormers) that add interior space: Same provisions as single-family houses (e.g. limits on roof coverage); and Additional interior space valuable for DADUs.

Councilmember Mike O’Brien’s backyard cottage legislation should be introduced to the Council soon for further consideration.