seattle backyard cottage blog

Backyard cottages (DADUs) provide opportunities for families, while increasing housing stock density and diversity. Continue reading for more information about Seattle's backyard cottage ordinance or contact us to find out if your lot is eligible for a backyard cottage..

Friday, October 26

owner occupancy requirement spotlight

What might it look like if the owner occupancy covenant were removed?

One developer explores the theoretical with a new independent condominium listings for a remodeled residence and a new backyard cottage.  As featured in Curbed

curbed seattle

Thursday, October 18


So now we know.  An appeal has been filed by the Queen Anne Community Council.  This will ultimately delay city council action by at least several months.

Wednesday, October 17

will a lawsuit delay implementation of the ADU EIS?

Stay tuned we should know by tomorrow.

Under SEPA, a 14-day appeal period follows the publication of a Final EIS. That appeal period will end tomorrow, October 18.  If no appeal is filed then the City Council will consider legislation to implement the proposed Land Use Code changes. Council will hold a public hearing. All Council meetings offer opportunities for public comment. 

Thursday, October 4

final ADU EIS issued

a backyard cottage in Capitol Hill

Almost two years on here is the final EIS report that studies the impacts of the following key changes to the land use code.

  • Allowing two ADUs on one lot
  • Removing the off-street parking requirement
  • Removing the owner-occupancy requirement and requiring one year of ownership when creating a second ADU
  • Modifying development standards that regulate the size, height, and location of DADUs
  • Increasing the household size limit for a lot with two ADUs
  • Establishing a new limit on the maximum size of single-family dwellings
To read the final EIS along with the preferred alternative click the following link. Final EIS

Whats Next?

The City Council will consider legislation to implement the proposed Land Use Code changes. Council will hold a public hearing. All Council meetings offer opportunities for public comment.


Further lawsuits are anticipated which will drag the process out likely until next year. Stay tuned for updates. 

City Preferred Alternatives

1. Number of ADU's on a lot:

City Preferred Alternative: Allow an ADU and DADU on lot while not requiring owner occupancy.

2. Parking: Remove parking requirement for 

City Preferred Alternative: No off-street parking required.

3. Owner Occupancy:  

City Preferred Alternative: No requirement for owner occupancy.

This is a real disappointment. The original proposal had required owner occupancy for a period of a year to minimize redevelopment pressure. The preferred method only requires that the lot has been under continuous ownership for a minimum of one year.  

4. Reduce minimum lot size:

City Preferred Alternative: reduce minimum lot size from 4,000 sq. ft. to 3,200 sq. ft.

5. Allowable cottage size increase:

City Preferred Alternative: Increase DADU size from 800 to 1,000 sq. ft. excluding garage and storage areas.

6. Additional Height:

City Preferred Alternative: Increase allowable height 1 to 3 ft.

7. Lot coverage Limit: Maintain.  

8. Rear yard coverage increase

City Preferred Alternative: Increase from 40% to 60%.

9. Rooftop features alternate: 

City Preferred Alternative: Allow

10. Location of entry alternate

 Allow entries on any façade with 10 ft min. from nearest lot line

11: Maximum Household Size:

City Preferred Alternative: increase the household size from 8 to 12 for lots with three dwelling units.

12: MHA fees would apply when an owner applies for a second ADU.

City Preferred Alternative: No additional fees or incentives.

13: Reduce pre-development costs by 10%.  

Under consideration outside of EIS scope.

14. Introduce a maximum FAR ratio:

City Preferred Alternative: Establish floor area limits for new single-family residences.

Saturday, September 15

backyard cottage open house Friday September 21st

Join us to learn more about backyard cottages and meet others who have built or are planning to build a backyard cottage. Friday September 21st from 4:30 pm to 7:00 pm.

Chris and Colette built this DADU as a short term rental.  Their cottage takes advantage of the sloping site to create a unique three floor design.  It features a large master suite and a smaller bedroom/office, a kitchen and living room with vaulted ceilings, and two baths. Sign up for our open house invite list for more details.

Monday, June 18

backyard cottage EIS comments due June 25th

Draft EIS study finds that the proposed code changes will reduce the number of DADUs built

The EIS provides a useful tool for community members and the city to evaluate the impacts of growth in residential neighborhoods. The information gathered can and should be used shape policy in our changing city. Given the information presented, we support Alternative 3 with its emphasis on maintaining the scale of existing development in single family residential zones. Most importantly the EIS finds that Alternate 3 will reduce the amount of natural occurring affordable housing lost to redevelopment. We feel that a moderate pace of scaled growth will lead to more equitable and environmentally sustainable Seattle that maintains a strong sense of place

Backyard cottages are a great addition to our city providing the low hanging fruit for increasing urban density while providing housing opportunities for families. The EIS study finds that backyard cottages increase housing options in areas that are deemed to have the highest access to opportunity. In fact we see this trend on an ongoing basis.  A majority of the cottages we design are being built as rentals.  And while the cost of construction is relatively uniform across the city, rental rates vary greatly.  As a result, the return on investment is higher for a cottage built in a more desirable neighborhood with higher rental rates.

As rental rates have increased so to have the number of backyard cottages built. Current rates of production are close to 150 new DADUs per year. The EIS analysis finds that Alternate 1 (no action) would result in the production of 1,890 new  DADUs, Alternate 2 (representing the broadest range of changes) would result in 1,820 new DADUs and Alternative 3 would result in 1,705 new DADUs being built in the next ten years. It is interesting to note, that of the alternates, the highest number of DADUs would be produced under Alternate 1 which represents no change to the current land use code.  Given those results, it would be hard to argue that the proposed changes are necessary to encourage DADUs. However, the EIS does provide the opportunity to suggest improvements through the comment process which runs through June 25th. All comments will be included in the final EIS report. To review the EIS document and to comment visit. DRAFT EIS.

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

1. Number of ADU's on a lot: Alternative 1 no action or Alternative 3 Allow an ADU and DADU on lot while maintaining the owner occupancy covenant.

DADUs  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. 

2. Parking: Remove parking requirement for ADUs. Alternative 1: no action.

There is already a parking waiver system which allows for conditions where the cost to add parking is expensive or otherwise infeasible.  If we are serious about building equitable communities we shouldn’t be caviler about parking.  Those who depend most on cars are the working poor and families with children. More than others, the working poor don’t have the luxury of having just one job in an urban center served by transit. They need a car to get to multiple jobs in dispersed locations, often in off hours.  Similarly, it is virtually impossible for families with young children to function in Seattle without a car. 

3. Owner Occupancy: Alternative 1 or Alternative 3

The EIS looks at the effects of removing the requirement all together for the sake of studying the impacts.  The original 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. However, owner occupancy should be required for all DADUs used short term rentals.  

4. Reduce minimum lot size: Alternative 3

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 3

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.  

6. Additional Height: Alternative 1 (no action)

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 neighboring 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 wanting higher height limits.

7. Lot coverage Limit: Maintain.  

Recognizing that yards do have a value both for families raising children and as green spaces and as a way to reduce stormwater runoff. 

8. Rear yard coverage alternate: Increase to 60% (Support): 

The proposed changes don't actually increase the total amount of lot coverage allowed. 

9. Rooftop features alternate (Support): 

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 therefor have no environmental impact but will facilitate good design.

10. Location of entry alternate (Support): the alternative to allow entries located facing the nearest lot line as long as the entrance is located 10 ft or more away.

11: Maximum Household Size: No change, Alternate 1 or 3

Alternative: increase the household size along with maintaining owner occupancy requirements.

12: MHA fees would apply when an owner applies for a second ADU.

MHA fees will discourage the creation of additional units.  It would seem better to require that additional units, if allowed, meet affordable housing guidelines.

13: Reduce pre-development costs by 10%.  

SDCI can start by assigning a designated reviewer for DADUs wich will eliminate inconsistencies and streamline the review process saving both time and money.

Additional alternative: SDCI can waive fees for DADUs with affordable housing criteria.

14. Introduce a maximum FAR ratio: Alternate 3

This is a big introduction into the EIS study.  Floor area ratio is the ratio of the gross area of a structure to the total lot area.  Currently, the FAR is not restricted in single family zones and size is restricted by setbacks and lot coverage. As shown in the EIS introducing an FAR limit will increase the number of smaller more affordable houses being built and reduce the destruction of naturally occurring affordable housing.

Thursday, May 24

backyard cottage bike tour - saturday

Join us for an informal bike tour of backyard cottages in Fremont, Greenwood, and Ballard this coming Saturday, May 26th. The ride will begin in Fremont at 9:30 am. Included in the tour will be four very different DADU garage conversions.  Contact us or sign up for our open house invite list for details

Thursday, May 10

ADU Draft Environmental Impact Statement (EIS)

Today the Seattle City Council released a ADU Draft Environmental Impact Statement (EIS). The public is invited to review and comment on this Draft EIS, which examines potential environmental impacts of proposed Land Use Code changes related to ADUs in single-family zones.


The City of Seattle proposes to remove regulatory barriers and make it easier for property owners to create accessory dwelling units (ADUs) and increase the number and variety of housing choices in single-family zones. The proposal involves Land Use Code changes that would allow two ADUs on one lot, modify existing off-street parking and owner-occupancy requirements, change development standards that regulate the size and location of detached ADUs, and that regulate the maximum size of single-family dwellings. Based on a decision from the City’s Hearing Examiner in December 2016, the city has prepared an Environmental Impact Statement (EIS) that analyzes three alternatives and identify the impacts of each alternative.

The public comment period for this Draft EIS extends through June 25, 2018. You can learn more about this proposal and provide feedback at Following the Draft EIS comment period, the city will prepare a Final EIS that includes responses to all substantive Draft EIS comments that address the environmental analysis. Comments on the Draft EIS stimulate discussion about how to change or modify the proposal to further protect the environment.

* ADUs include backyard cottages, known as detached accessory dwelling units (DADUs), and in-law apartments, known as attached accessory dwelling units (AADUs)

Saturday, April 28

how big? - a look at Seattle's backyard cottage rules

The first question we typically answer is what can we build? As the cost of building a backyard cottage is not insignificant, it makes sense to make a careful analysis of both the governing regulations and the potential for each site. It seems obvious that an erroneous or incomplete knowledge of land use and building codes can lead to expensive mistakes and delays.  What might be less obvious is that lack of informed planning may also lead to a failure to realize the full potential of a particular site and use. 

FAQ: backyard cottage allowable size - in Seattle backyard cottages are limited to 800 sq. ft. in size -- referred to in the land use code as Gross Square Footage.

This 3 bedroom cottage has a footprint of 800 sq. ft. and a full basement

This Columbia City property is shared by two sisters who are planning to build a family compound with separate houses. They were worried that an 800 sq. ft. cottage would not be adequate for a growing family. They felt that it was important for the cottage to have a kitchen, living, full bath, and 2 bedrooms on the main level in addition to a separate family room, office and 1/2 bath.  A tall order for 800 sq. ft..

For them, the solution was to add a basement level -- as below grade basements are not counted towards the allowable area. This also reduced the height and bulk of the cottage which is another consideration when adding a DADU to a typical Seattle lot. Fortunately, the owners have a couple of things working in their favor. One is that they have a relatively large lot which allowed them to build 800 sq. ft. on one level. The other is that the owner's father is a contractor and who built them a scaled mock-up that we could use to help model the visual impacts to on their yard. In this case, the cottage was designed to be just large enough to block the view of a series of new apartment buildings, but not so large as to adversely shade their yard. 

FAQ: backyard cottage allowable size - storage areas, attics, garages, and carports are included in the allowable area.

It is important, but not always easy, to get a handle on how a cottage will feel in the backyard. We often start by pacing out the dimensions of typical cottages with our clients. We think of 400 sq. ft. as being the minimum footprint for a single level 1 bedroom cottage. However most cottages we design have a 2nd floor to maximize living area while keeping the footprint to a minimum. 

Just getting started? We recommend attending one of our backyard cottage tours, which happen periodically throughout the year. They provide an opportunity to get a sense for the size of DADU's both inside and out. You can use the widget at the top of the page to sign up for our open house invite list.  

Looking for backyard cottage ideas? Please visit our web page at the following link.


Wednesday, April 4

backyard cottage rule changes

This morning SDCI staff briefed the city council on proposed changes to the land use code affecting backyard cottages. The changes are part of omnibus code update, a collection of amendments that are relatively small in scale, and have a limited scope of impact, into an “omnibus” bill. 

If you were hoping, as we were, for clarification on gross square footage or parking or other hot topic items you will be disappointed. However, if you live in a shoreline area you can now build a backyard cottage. The original legislation concerning backyard cottages prohibited DADUs on lots if any portion of the lot was within a shoreline district.  It is not clear what the intent of the original legislation was. Now that it is proposed to be eliminated, should we expect an explosion in the number of beach cabanas in Seattle?  Unlikely, since 2009 we have only spoken with two potential DADU builders who were impacted by this restriction. Of course, they will be quite happy.

Meanwhile, the more significant proposed DADU code changes, those that are part of the ongoing EIS process, are scheduled to go before Seattle City Council this summer.

Sunday, March 11

backyard cottage - would you move into your own backyard?

The owner built this backyard cottage as a rental but fell in love (with the cottage) during the design process and decided to rent out his house instead.  

This backyard cottage features an open floor plan on the ground floor with a kitchen, living and powder rooms that open with accordion doors onto a patio with a gas fireplace.  Upstairs is a master bedroom complete with a kitchenette, and a bath with laundry room.  The overall strategy with this backyard cottage, as it is with most of our designs, is to keep the structure simple allowing a larger percentage of the budget to be spent on finishes. The height and size of DADUs is limited based on the size of the lot. This lot was particularly small limiting the allowable footprint to 294 sq. ft. 

Ceramic tile accentuates the entry area.  The view from the entry towards the kitchen and patio beyond.

The kitchen is located along one wall is both compact and simple.

Accordion doors open up the cottage to the new patio with gas fireplace.

A movable kitchen island is the perfect accessory to the compact kitchen.  Exposed wood joists add warmth and texture in contrast with the concrete floors.  The joists were spaced to accommodate the owner's weight lifting rack.

Where some houses may come with a man cave this DADU features a "man wall" with big screen tv, electric fireplace, weight rack and the ultimate amenity, beer taps.  A keg fridge is located behind the wall in the under stair space.  

A door located at the bottom of the stairs allows for the two floors to be used independently.

The city of Seattle limits both the eave and ridge height of cottages allowing greater height for a gable roof which we took advantage of to good effect. 

The master suite features vaulted ceilings and abundant light. A kitchenette allows this room to be used separately from the first floor.

The shower is tucked into an under eave space. 

The master bath features vaulted ceilings and skylight.  A laundry room is tucked off to one side under the eaves.

The owner built a new patio with a gas fire place.  The stairs from the house were rebuilt align with the cottage.

Tuesday, March 6

backyard cottage workshop tomorrow - Wednesday, March 7th

Would you like to learn more about backyard cottages and meet others thinking about building a backyard cottage?  If so you might be wondering, can I build a backyard cottage on my lot and how much does it costs to build a backyard cottage?  To answer these questions we periodically assemble experts in the design, construction and of financing backyard cottages. Our workshops offer a unique opportunity to have your questions answered in an informal setting. 

backyard cottages for fun and profit   Wednesday March 7th,  from 7:00 to 9:00 pm, Blue Building Room 1. Phinney Neighborhood Center 6532 Phinney Avenue North

Backyard cottages can be used for many things including housing a family member or as a short term rental.  Join Microhouse and Ncompass Construction to learn more about backyard cottage design, construction, and use. Bring your ideas, after the presentation we will have plenty of time to answer questions about the specifics of your project. 

Microhouse and Ncompass Construction
$15 PNA member, $20 Public