Backyard Cottage Quick Start Guide


Are you considering building a backyard cottage? We've put together a Seattle Backyard Cottage Quick Start Guide* to help homeowners better understand Seattle's citywide backyard cottage ordinance and the opportunities available to them.

The first step is to figure out whether or not your lot is large enough to qualify for a backyard cottage. The chart below outlines the minimum requirements for lot area and dimensions. lot_dimensions

Minimum Lot Size 4000 sq.ft.
Minimum Lot Width 25 feet
Minimum Lot Depth 70 feet

spacer The next step is to figure out what portion of your lot is buildable under the backyard cottage ordinance. Setbacks, yard requirements and maximum lot coverage all factor into whether or not a cottage is feasible. BUILDABLE-AREA

Setback from lot lines 5' unless adjacent to an alley in which case the setback is 0
Setback from other structures 5'
Maximum Lot CoverageSMC 23.44.010 Lots less than 5,000 sq. ft. - 1,000 sq. ft. + 15% of lot area
Lots 5,000 sq. ft. or more - 35% of lot area
Maximum Rear Yard Coverage 40% of the area required for the rear yard.
Maximum Front Yard Coverage Cottages not allowed in front yard.
Off Street Parking SMC 23.44.016 One space per dwelling unit required - some exceptions apply.
Entry Location May not be located on the side facing the nearest lot line unless that lot line abuts an alley or other public right of way.

spacer Once you've verified that your lot can accommodate a backyard cottage the next step is to take a look at the the floor area and height restrictions in order to determine if you can meet your objectives within those boundaries. GROSS-FLOOR-AREA-3

Gross Floor Area SMC 23.86.007 800' square feet max.Gross Sq. Ft. is measured from interior finished surface to interior finished surface. If you are planning a two story structure the floor area of each story counts toward the total.

spacer There are three factors that set the height limit for your cottage, the width of your lot, the type of roof you choose and the height of your home.

Lot width
< 30' 30'-35' 36'-40' 41'-50' 50' <
Max base height 12' 14' 15' 16 16
Max height with pitched roof 15' 21' 22' 22' 23'
Max height with shed or butterfly 15' 18' 19' 20' 20'
Max height above peak of existing home 15' 15' 15' 15' 15'


CAST Architecture tim@CASTarchitecture.comFeel free to email me with any questions you may have regarding Seattle's Citywide backyard cottage ordinance
Seattle Department of Planning and Development (DPD) Seattle Backyard Cottage OrdinanceThis is the definitive legal document covering Seattle Backyard Cottages.
DPD's Land Use Q&A ServiceAny ambiguities or clarifications unanswered by the ordinance document (above) can be addressed through the DPD's Land Use Q&A Service
DPD CAM 116B - Establishing a Backyard CottageThe DPD's client assistance memo (CAM) outlining the citywide backyard cottage ordinance. CAMs are guides intended to help people navigate the building permit processes in the city of Seattle.
A Guide to Building a Backyard Cottage in Southeast SeattleThis is an out of date but very useful guide put together by the DPD for Backyard Cottages in Southeast Seattle. The ordinance the guide was written for has changed (proceed with caution) but the value of the guide is still intact. It covers many of the issues you are likely to encounter and does a good job of mapping out design considerations you should be aware of.

*This guide is intended as an overview of the backyard cottage ordinance and does not include detailed conditions and restrictions that may affect individual properties. Please note that the guide was created in 2010 and that zoning codes may have changed since then. As such, it should only be used as a basic starting point for planning. If you would like to move forward with the design and permitting of a backyard cottage for your home we recommend careful scrutiny of the entire ordinance and the assistance of an architect or design professional.spacerDownload guide as a printable pdf Download guide as a printable pdf spacer