Backyard Cottages

Summer time gathering of the whole CAST

CAST crew celebrating Summer! The siren's call of Seattle's summer has brought everyone back to town.  Last night, we celebrated our the solstice (a little late), the return of Holly from Sonoma and Forrest from Madrid, and had a little send off for Gunnar who is heading back to Norway's midnight sun.

CAST has a few other reasons to celebrate:

We're starting a two projects in Mazama (schematic design images upcoming).

Kenny's house is nearing completion:


Our first modular home on Bainbridge Island for Michel and Chas just went on the market this morning:


And the Mazama Ranchero is going to be published in a few magazines this fall, as well as the Lichtenstein cottage in a feature about Small Spaces:


Plus, Rainier Beach Urban Farm and Wetlands is in permit, ready for construction this fall:


Happy summer, everyone!


This new home was permitted under Seattle's citywide backyard cottage ordinance (which is rapidly approaching it's second year anniversary). The existing home, with a large corner lot and alley access, was an ideal candidate for a backyard cottage. The site allowed both the existing home and new cottage to enter from separate streets, have separate outdoor living areas and maintain a great deal of privacy from one another.

The owner desired a modestly scaled 800 square foot structure with exterior massing that followed the traditional lines of the existing home and a modern, light filled interior that opened to a private courtyard and was suitable for entertaining guests. The floor plan centers on a double height dining room with clerestory windows, sleeping loft and a large 4 panel door that frames views of the private courtyard and terraced garden. The cottage features radiant floor heating, an efficient on boiler with integrated solar hot water collection and a 1500 gallon cistern for rainwater catchment.

The homeowner served as the general contractor and invested considerable sweat equity which allowed the total project cost to come in at just under $100,000 ( ! ).

View from the dining room into the kitchen.

1,500 gallon cistern for rainwater catchment.

View from the kitchen into the dining room and living room.


CAST architecture recently participated in a Seattle City Council discussion regarding backyard cottages. The meeting began with a presentation of backyard cottage statistics that were gathered during the first year of the city wide backyard cottage ordinance. Following the presentation participants discussed working with the ordinance in practice and suggested potential improvements that could be made to the ordinance. You can view a video of the entire discussion at Backyard Cottages: 1 Year Later

There is also a backyard cottage annual report available to download from the DPD's website: Backyard Cottages Annual Report - April 2011

Of particular interest was the number of cottages permitted in the first year (57) and their relatively even distribution throughout the city. One of the primary concerns opponents had expressed in opposition to the ordinance was a fear that dense concentrations of cottages would "take over" single family neighborhoods causing widespread parking and privacy issues. The fear was so potent and adamantly expressed that at one point during the development of the ordinance city council members considered placing limits on the number of permits per year (50) and limits on the number of cottages allowed in any given area. Thankfully, neither limit was written into the code and the fears have been proven to be unjustified thus far.

A few other interesting issues that came to the surface during the discussion were:

  1. The relatively high costs of constructing a backyard cottage makes it difficult for home owners to see a return on their investment if they hope to use a cottage to generate rental income. In general it was felt that backyard cottages were an important new housing typology for the city and that the cottages are a valuable addition to the city's rental stock. It was proposed that the city should consider incentives that would help lower the cost of constructing a cottage and help encourage their creation. A reduced permit fee and property tax credits are two areas I think the city should review.
  2. The feeling that the off street parking requirements (2 spaces) was in most cases unnecessary and to the detriment of green space and usable yards. One idea put forth was to loosen the parking requirements by making it easier to obtain a parking waiver on streets where parking is not an issue.
  3. The base height limit was thought to be a bit too low and creates unreasonable difficulties for the construction of two story structures. During the public comment portion of the meeting architect Jim Burton suggested changing the datum to which the base height could be measured (top of plate) to add a bit to the base height limit and encourage homeowners to exceed minimum requirements for insulating roofs and ceilings. The overall height limit was thought to be adequate with the exception of the following issue:
  4. The current ordinance sets the height limit to 15' above an existing home. This was thought to be problematic and unfair in the case where the property owner's lot has a significant slope up behind the existing home.
  5. The current ordinance does not allow for a backyard cottage to be built on a through lot (a lot with a street on both the front and rear lot lines of a property). This was generally thought to be a mistake in the writing of the ordinance and that the ordinance should be revised to allow cottages on through lots.

All in all it was a fun and informative meeting. Kudos to the city employees key in the development of the ordinance and to Sally Clarke and the city council for passing the ordinance unanimously. After the first year of real world testing the ordinance has proven to be a resounding success.

Backyard Cottage Tour

The Widner Cottage is going to be open to the public twice this summer for tours:

First, the Phinney Neighborhood Association's Home and Garden Tour will roll through on June 12th, from 11-4 pm (see link).

Second, the Cottage will be featured as the AIA Seattle's Open House on July 17th from noon to 3 pm.  More information here.  As part of the tour, the house will be published in Seattle Magazine, in the Northwest Home section in July.


beam-ends Kate and Ric have begun construction on their backyard cottage... They have been working hard the last few weeks and have enlisted the help of a few friends and colleagues along the way. A few key players have been helping guide us through the process:

  • Rusty Borromeo of Borromeo Construction LLC is providing his general contractor and construction expertise
  • James Jenkins of O'Brien & Company is contributing his green building knowledge and will be our Built Green Verifier  - we are aiming for 5 star Built Green certification
  • Cory Fraser of LFD Structural Engineering LLC provided the calculations and engineering for our plan set

Ric has been doing a wonderful job of photographing the process and has put together a few galleries of the construction process thus far (all images in this post are © 2010 Ric Cochrane). He has also agreed to write up a blog post on the experience thus far - so stay tuned for that!

DECONSTRUCTION GALLERY An existing shed (that was a bit worse for wear) was painstakingly deconstructed and all reusable and recyclable materials were sorted and stacked deconstruction

LABOR OF LOVE - THE FOUNDATION Digging in the dirt and other fun activities - the true definition of 'sweat equity!' slab

LUMBER FROM THE BONE-YARD Salvaged beams, columns and decking are being purchased from Bruce Borjesson of Pacific Resources boneyard

Phinney Ridge backyard cottage

phinney ridge backyard cottage We have been working with a couple who are planning on moving out of the original house, and into a new backyard cottage.  We're pushing the limits within the ordinance--almost exactly 800 square feet--in order to build a 2 bed room, bath and a half cottage. Although the house is small, the spaces inside feel just right.  And we'll be able to include a lot of high finish touches and crisp details because we aren't spending money on lots of square footage. Having a finite perimeter and volume really focuses the mind on the priorities of the design.

The character of the house the client's wanted is very craftsman and the scale and roofline fits right in with the neighborhood in general--certainly not the scary developer vision that opponents of the ordinance summoned during the public hearings.  It reinforces that these projects are for people with a vested interest in both their property and their neighborhood and are very sensitive to the impact on their neighbors.

Here is another view which shows off the walkout patio off the dining space, the entry mudroom and the band of windows that wrap the living room, dining and kitchen:

seattle backyard cottage in phinney ridge

We are also going to integrate a rain water harvesting system, radiant floors on a super efficient combination boiler, vaulted ceiling upstairs, and a extra height crawlspace with a rat slab to make up for some of the storage space lost in the downsizing.  For floor plans, follow the jump below:

First floor plan:


Second floor plan:



7 We've completed the second round of design on our CAST architecture case study backyard cottage.

The plan has been fine tuned to optimize it for advanced framing. We adjusted the spaces to work better with Kate and Ric's needs and have started looking at potential materials and finishes.

We've also started talking about systems - at this point everything is on the table, solar hot water, energy efficient boiler, hydronic floor heating systems, rainwater cistern for flushing the toilets and watering the yard, super insulated walls...

I suspect that our choices will narrow as the reality of our budget forces us to separate the wheat from the chaff. Right now however, the possibilities seem limitless!








The Seattle channel recently interviewed myself and CAST clients Kate Lichtanstein and Ric Cochrane regarding the backyard cottage we are currently working on together. They included our project in a broader story that profiles an owner of a recently completed backyard cottage and gives a basic outline of the new Seattle backyard cottage ordinance.

Seattle Channel Video can be played in Flash Player 9 and up


Are you considering building a backyard cottage? We've put together a Seattle Backyard Cottage Quick Start Guide to help homeowners better understand what they can do on their lot…

UPDATED AUG. 8th 2019

08/08/2019 - Now that new legislation is in place we’ve updated Quickstart Guide to include the 2019 land use code changes.

Please keep in mind that this information is intended as a high level primer for the code that governs backyard cottages in Seattle. 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 we recommend careful scrutiny of the governing land use code and / or the assistance of an architect or design professional.

Download guide as a printable pdf


Demographics of a Seattle Backyard Cottage

demographicsWe've seen an unexpected level of interest in backyard cottages in the 2 months since the new ordinance has been in effect. Perhaps the most interesting thing about the projects is the diversity of needs for each one... We have a young couple with a small house on a large lot that would like an outbuilding with a workshop and guestroom. We have a couple planning to build and occupy a cottage in their backyard in order to open up their home for their children and grandchildren to live in. We have a third couple who have separated but are committed to raising their children together. They currently live in the same house and believe that adding a backyard cottage to the property will maintain the proximity they need to raise their children together while providing them the space they need as individuals.

In a bit of a surprise, we have yet to see anyone looking to build a cottage for the sole purpose of rental income. Although one of the guys here at the office has been running the numbers and is strongly considering building a cottage for rent in his backyard.


intro-image We've completed the first round of design on our CAST architecture case study backyard cottage.

Kate and Ric's cottage is intended to serve as an art studio, workshop and guest house. It is also designed so that it may function as a rental home if needed. Our initial round of planning looked at how the spaces might work as a rental thinking that those functional requirements would be more restrictive than the requirements for an art studio and workshop.

Elements common to all three schematic design options:

All three options place the cottage at the SW corner of the site, chosen for it's relationship to the more public areas of the existing home and for an opportunity to create a shared outdoor room for both the cottage and the home. They all have a gable roof which was chosen for the height bonus allowed in the ordnance and to help marry the form of the cottage to the form of the existing home. All three options have the kitchen, living and bath rooms on the first floor and a bedroom loft on the second floor. Another feature common to all the options is the use of salvaged galvanized steel scaffolding components (see image below) which we plan to use as treads for ladder to the loft spaces.



This design incorporates an existing garage which more or less sits on the South and West property lines. The city land use desk (walk in) indicated that it was probable that we would be able to grandfather the building envelope of the existing garage into a new backyard cottage but they were unwilling to guarantee it. They recommended that we go through formal land use approval early in the process. Regardless of their final call we did know that we would have to stick within the building envelope of the garage for all portions of the backyard cottage that did not conform to the new ordinance. The potential advantage of using the existing garage is that it would allow us to use up less of the yard space for our new structure.


This drawing illustrates the site plan and floor plans. The existing garage is the portion of the structure that bumps out to the south and the west.


This is a view of the cottage from the SE. You can see the envelope of the existing garage on the south side of the structure.


A view from the NE looking through the shared outdoor room.


A view looking from the dining room, past the scaffolding ladder and into the living area.


A view from the living room into a private shade garden inspired by small Japanese courtyard gardens and created in the 5' setback from the lot line. a four foot concrete wall and cedar fence above create a very private and intimate indoor/outdoor space.


A view from the street.


The major element in this design is the creation of a covered outdoor workspace to the south of the cottage.


The covered patio to the south provides a sheltered outdoor workspace. The loft space is pulled back from the east wall allowing two stories of light to fill the first floor studio.

option2-courtyard-from-SView from the SE


View from the NE


Loft space


This scheme ended up being the winner with Kate and Ric. They felt it was the best fit for their needs in terms of layout and size. It features a simple open plan on the first floor and a second floor that is more private than the lofts in the first two options.


Pass through doors and a simple plan define this scheme.


View from the SE.


View from the NE.


Entry from shared outdoor room


Looking toward the kitchen and dining room.


Bath with a private shade garden.




view_2 We can't seem to get enough of Seattle's new citywide backyard cottage ordinance...

In addition to the two custom solutions we are currently working on we've also started up plans for a prefabricated backyard cottage. Designed to be trucked to your home and assembled in minimal time, this compact home is your ticket to instant gratification. If you are looking for a space to make art, stash guests on extended stays or earn a little rental income - look no further...



The first floor features the living, kitchen and dining rooms as well as a bed and bath. A double height space over the living room and a portion of the dining room brings light deep into the interior and provides a feeling of spaciousness.


The second story loft looks out over the living and dining rooms and has space for an office, a guest bed and overflow storage.




The cottage is designed to ship on a single semi and assembled in minimal time. We're currently working with a regional manufacturer and a local builder to see if we can get the price point to come in under what you would pay for a similar site built structure... Send us an email or give us a call if you would like us to keep you posted.

Seattle Backyard cottages - The the dpd posts a new cam

CAM-116B The Department of Planning and Development (DPD) has posted a new client assistance memo (CAM) to outline the citywide backyard cottage ordinance. CAMs are guides intended to help people navigate the building permit processes in the city of Seattle.

CAM 116B, Establishing a Backyard Cottage (Detached Accessory Dwelling Unit) "This Client Assistance Memo (CAM) explains the requirements and process for establishing a detached accessory dwelling unit (also called a DADU or mother-in-law unit) on an owner-occupied Single Family zoned lot in southeast Seattle."

If you are considering building a cottage in your backyard it is still worth reviewing the DPD's older, more comprehensive (but now somewhat inaccurate) publication: "A Guide to Building a Backyard Cottage in Southeast Seattle."

BLOGGING A SEATTLE BACKYARD COTTAGE - a CAST architecture case study project

house Greenwood resident Kate Lichtenstein contacted us last spring to help her design a backyard studio / guest house for her modest 650 square foot 1920's one bedroom home (shown above). While the home's scale fits nicely with Kate's desire to have a simple and ecologically responsible lifestyle it falls a little short when it comes to a rough and ready workshop space for art, bicycle repair, ski tuning and building projects. Kate's home also lacks the space for a home office / guest room - something that she would like to integrate into the new structure.

Our initial goal was to have her project under construction by late summer 2009 but we were unable to get the project off the ground by that time. In hindsight, the stalling of the project turned out to be a stroke of luck...

In March of 2009 Seattle Mayor Greg Nickels proposed legislation that would allow Seattle homeowners to construct backyard cottages on their property. The legislation was reviewed and ultimately passed by the Seattle city council on November 2nd 2009 (with a 9 to 0 vote too! Kudos to Seattle voters for electing progressive urbanists for city council members!).

For Kate the ordinance has opened up new possibilities for a structure that can both accommodate her current needs and provide a potential source of income as a rental unit if her finances ever fall on hard times. Besides allowing for a legal detached rental unit the ordinance also allows for the construction of a two story structure – an arrangement that will work well for Kate’s needs and will help to preserve the spaciousness of her backyard.

Kate is planning to build with a mind toward sustainability and has a special interest in using recycled building materials whenever possible (she is, at this time, planning to write a parallel blog on the topic of recycled building materials). For us at CAST architecture Kate's project is an exciting chance to test out the new backyard cottage ordinance and work with a client who is committed to building green. We see her project as an excellent opportunity to provide the general public with information about the process of designing and building a backyard cottage in Seattle. Kate and her partner Ric Cochrane are always game for an adventure and have graciously agreed to allow us to share their experience with you. To that end, we are planning to blog about Kate's project as we travel through the design and construction process. Please subscribe to our feed if you would like to follow along in future posts…


Breaking---Backyard cottages pass 9-0!

The ordinance  to allow backyard cottages in the other three quarters of Seattle just passed 9-0!  The council's comments focused on the exhaustive community outreach, successful pilot program and benefit of having this housing choice for Seattle. Excellent work by the planning commission, DPD and council.

Usually, the city's process oriented decision making can be cumbersome, and having spent hours in meetings, testifying, and communicating with council, I feel vindicated that our involvement has helped in some small way to bring some innovation to the Single Family zoning.

We're excited to design some of these--in part because of the opportunity to foster multi-generational housing, and the option of building a smaller free standing structure rather than building an addition.  Plus, it is a really fun scale--I think more people will be thinking about bonus studios rather than housing units.