Chris Walter, @ChrisWPhoto, talked with Matt Hutchins about the significance of Accessory Dwelling Units (ADUs).

At CAST architecture, we have been focused on ADUs for more than a decade. They're fun to design, perfectly fit a niche for new housing in established neighborhoods, and provide many benefits for owners and residents.

https://www.youtube.com/watch?v=PJaLht9v5Yw

CAST’s Cedar Cottage is a City of Seattle Pre-approved DADU. Our vision is to adapt the high-design cottage, simplify it, and make it accessible.

See more at www.castcottages.com

“Part of the reason we love backyard cottages is just the opportunity. If you have a home with a possibility for a second house – it could be whatever you want it to be – a studio, a place for grandma, a rental, and having that flexibility is huge. We have people who have it as an Airbnb, or a long-term rental, as a place for their kids and then their retirement home. This flexibility is fantastic. It opens up so many opportunities in this great city.”         -- Matt Hutchins, AIA, Certified Passive House Designer

Backyard cottages = Flexibility and Opportunity

Published at Seattle’s Daily Journal of Commerce https://www.djc.com/news/ae/12162400.html

ON THE BOARDS - METHOW VALLEY’S RIVERSMeet WINTHROP proposed MIXED-USE BUILDING

RiversMeet, a proposed mixed-use project in the town of Winthrop in Washington’s Methow Valley, is positioned to become the upvalley entrance to “old downtown.” The site is a challenging set of narrow parcels overlooking the confluence of the Methow and Chewuch Rivers.

CAST’s client, Peter Goldman, as part of his development proposal, intends to request the town make zoning changes to allow for long-term rentals in the commercial district. RiversMeet is envisioned as a template for how buildings can work within Winthrop's westernization code while striving for high levels of sustainability and providing more inclusive housing options.

The program will provide two 2-bedroom residential units overlooking the river, with approximately 1,870 SF of pedestrian-level retail space. The second floor incorporates 1,870 SF of office space. The second floor incorporates 1,870 SF of office space, continuing the client’s tradition of renting below market rate to community non-profit businesses.

Team
Client: Peter Goldman and Martha Kongsgaard
Architect: CAST architecture
Builder: North Star Construction Company  www.Northstarbuilds.Com
Civil & Structural: DCG   www.dcgengr.com   
Electrical: TFWB   tf-wb.com
Environmental:  Grette  www.gretteassociates.com  
Geotech: Geoengineers  www.geoengineers.com/ 
Mechanical: Ecotope   www.ecotope.com 
Survey: Tackman   www.tackmansurveying.com

Give Middle Housing a shot!

Matt Hutchins’ comprehensive discussion, at Medium, of the Washington state Model Code for Middle Housing and how we can have it produce more housing in line with HB1110.

In HB 1110, the State Legislature read the will of the people and demanded that we tackle the housing crisis more proactively by allowing Middle Housing in most cities and towns. Washington State Department of Commerce has created a basic zoning template that supersedes local code if town planners balk at updating their own code to comply. The draft version of that Middle Housing Model Code is out for comment (comment here by December 6th!). I have analyzed the real world implications of how it would regulate new housing and how we can tweak it to better support the creation of townhouses, flats, and infill development.

Here are my recommendations:

1. Allow Middle Housing to be larger than single family houses: more lot coverage, smaller setbacks, and make them taller.

Diagram of current allowable single-family building sizes in 6 cities to illustrate that the Model Code’s Floor Area Ratio system is actually more restrictive.

It seems like an obvious point that the bulk of a building or buildings for up to 2, 4 or 6 households might be larger than one with just a single household, but a close look at some of the cities governed by this new legislation reveals that the draft code is MORE restrictive than current codes. It would effectively be a downzone in structure size in order to house more people. That isn’t a good trade, and for all the proof that Middle Housing has wide ranging benefits, we should have a code that supports it.

Middle housing is not just a bridge between the densities of single-family neighborhoods and denser areas, it is also a incremental increase in size between those building types.

2. Measure lot coverage, not FAR

There is a policy conversation about two methods for measuring building size: 1) lot coverage X height vs. 2) lot size X Floor Area Ratio. The draft code uses FAR for Tier 1 and 2 cities (the larger cities and the municipalities around them), and Lot Coverage for Tier 3 cities (smaller cities).

In the six Tier 1/Tier 2 cities I picked to analyze, five use lot coverage not FAR. The model code should follow suite. It is easy to implement, understand and compare apples to apples to existing codes.

Diagram of small cities buildable footprint illustrates how extra flexibility in lot coverage will translate to new housing for those communities.

Meanwhile Tier 3 cities, the code uses lot coverage to provide flexibility for how to develop successful infill housing, because lot coverage isn’t the critical threshold, the market is. I think this part of the Model Code will be actually be good for many smaller jurisdictions that are struggling with housing cost and access.

3. Set thresholds by looking at what can be feasibly built, not what might be politically expedient.

Illustration of all the new building types and whether they would be viable under the draft Model Code for typical lot sizes.

There is often a disconnect between how planners see development standards and how developers implement them. But ground truthing the code, when it is a draft, to understand the inevitable determinative impacts on the housing types that will get built, is the key to making the good development we want to see also the easiest to build.

Using a typical 5000 sf parcel zoned under the new code for 4 units, applying the FAR, we can build 4000sf. It becomes immediately apparent that many of the housing types we’re hoping for will never materialize and other types are going to yield less that then maximum number of units. Of the six types, I would expect the only feasible project is three townhomes. It is unlikely we’d generate very many 1000sf townhouses, 1200 sf triplex units or courtyard apartment buildings under the added cost of the IBC compliance.

The FAR needs to be up between 1 and 1.2 before we’d see the fourth townhome, or an apartment building.

4. Lean into making the most efficient and affordable housing form (small apartment buildings) the default infill Middle Housing type.

Our Spokane Six on the left works today, but wouldn’t be viable under the draft Model Code. This illustration shows that it would need to be 21% smaller.

Small apartment buildings have significant headwinds when it comes to financing, construction and operation. They also are the greenest, most efficient, context friendly and often least expensive forms of housing. They are also the best for preserving usable open space and landscape for large trees. They are the lowest common denominator building block for tackling the housing crisis. If the code works for those, then the other forms, like ownership townhouses, will work too.

When we tested our recent Spokane Grand sixplex, using the new Model Code, we discovered that we’d have to reduce the size by 21%, loose one of the porches, and downgrade the units from family friendly two bedrooms to one bedrooms. The pro forma for the development fell apart. If it can’t work in Spokane, with low land cost, reasonable construction cost, steadily climbing rents, there is very little chance these buildings would be viable in Puget Sound or other Tier 1 and 2 cities.

Without zoning incentives to build apartments, the market will continue to underproduce less expensive rental housing, even if we see some new ownership townhomes.

5. Reduce parking minimums.

Parking is always the cart that drives the horse. We have a housing problem not a parking problem.

So much has already be said and written about the high price of parking mandates, so I’m going to appeal to pure geometry.

On residential lots, designing for parking is step 1, before you even start to conceive of a building. For a sixplex on an alley, where parking is required, one space per unit arranged along the alley would require a lot width 56' feet minimum, which is wider than most urban lots. In order to provide the parking, much of the back yard is overtaken with pavement, more than 1/3rd of the site, lessening the quality of life for residents, creating stormwater issues and additional costs.

Without an alley, it is always worse; more than half of our typical lot is parking or driveway.

6. Regulating aesthetics on small neighborhood buildings is unnecessary micromanagement.

Strike this section. Or don’t. It is really so milquetoast that compliance isn’t an issue, but there will be lots of overlap/conflict with local codes that do regulate these simple aesthetics. Most townhouses are less that 20 feet wide — does a building’s design need to change every time there is a door? It is so fussy. In the interest of less bureaucracy, we should stamp out regulatory creep preemptively.

A Model Code that works.

The State’s Model Code is an opportunity to create a baseline for Middle Housing but it has to work. And this draft code would be so much more effective if it wasn’t second guessing its own mandate.

A final Model Code based on incremental increases of size over current single family structures, lot coverage not FAR, without parking minimums and design prescriptions, which allows builders the flexibility the make the homes people need, is the right direction forward for a statewide standard.

New sedge backyard cottage: 3 bedroom DADU

At 997 net square feet, the Sedge Cottage is a highly livable footprint that provides well-daylit space for living, necessary storage, flexibility on many sites, and two covered outdoor porch spaces. Within its compact form, the design features three bedrooms and two baths, a galley kitchen with a peninsula and plenty of storage. It features a bedroom and 3/4 bath on the main level that works well for an aging parent, as a guest room or work-from-home office. Standard, wood-frame construction, vented shed roof, slab-on-grade foundation, the careful placement of windows, and a simple exterior allow for low-cost construction without sacrificing durability, function, or style.

The design is under the height limit and can fit on the smallest lots, around trees, or on sloped lots, with space for adjacent parking if desired. The outdoor covered area is perfect for a BBQ and the cottage can be oriented toward the principal residence for multi-generational living around a courtyard. The front porch clearly marks the entry of the accessory dwelling.

The design targets 4-Star Built Green, with details for reduced air infiltration, energy-efficient heating, cooling, and water heating systems, passive solar heat gain in window/shading in summer, low-VOC finishes, no fossil fuel appliances, and all LED lighting.

See more at CASTcottages.com

New Sitka Cottage: 3-bedroom DADU

At 1,000 net square feet, the Sitka Cottage features three bedrooms and two baths upstairs, an open living room and kitchen, storage, and an additional powder room tucked away on the first floor.  It fits flexibly on many sites with a walk-out terrace off the living room/kitchen. The three bedrooms upstairs are reasonably sized and work well for a family. Standard, wood-frame construction, vented shed roof, slab-on-grade foundation, careful placement of windows, and a simple exterior allow for low-cost construction without sacrificing durability, function, or style.

The design is under the height limit and can fit on standard to small lots, around trees, or on sloped lots, with space for adjacent parking if desired. The cottage can be oriented toward the principal residence for multi-generational living around a courtyard. The front door is on the corner and can be placed on either the short or long side of the design, depending on site orientation.

The design targets 4-Star Built Green, with details for reduced air infiltration, energy-efficient heating, cooling and water heating systems, passive solar heat gain in window/shading in summer, low-VOC finishes, no fossil fuel appliances, and all LED lighting.

See more at CASTcottages.com

Cross-Laminated Timber Berm House in Washington's Methow Valley

The Berm House is a private residence that doubles as the common house and gathering space for a 19 house mixed-income community in Washington’s Methow Valley. The house is set into the landscape, with a panoramic view of the farmland down valley, but hidden from the road by a berm that ramps up onto and across the roof. 

The south-facing building orientation optimizes winter solar exposure coupled with large overhangs to protect from snowfall and the intense summer sun. The home is post and beam structure with a cross-laminated timber (CLT) roof prefabricated in northeastern Washington. The design incorporates Passive House principles including managing seasonal heat gain from solar exposure, advanced air sealing, and mechanical ventilation. Thermal bridges are minimized by wrapping the house in continuous external insulation, including structural EPS under the foundation, isolating the home from outdoor temperature swings. The earthen roof adds thermal mass, wildfire protection, and a promontory to take in the down valley vista.

The great room portion of the house was designed for friends and neighbors to gather, share meals, and be a social center for the community. Off the great room, a five-foot wide hall leads to three guest suites and the primary suite. The uncomplicated and efficient floor plan shows a clear division between the private and public spaces. The mechanical room, pantry, storage, guest bath, and laundry spaces are arranged along the berm side of the house’s section.

The material palette is predominately warm woods. The CLT ceiling and glulam posts and beams were manufactured nearby, and a coffee table and kitchen bar were crafted locally from a fir tree felled on the property. The exterior employs the Japanese shou sugi ban preservation technique. The boulders throughout the site and as part of the berm were pulled from the site and placed by the owner. 

Team
Owner: Lee Whittaker
Methow Housing Trust
Architect: CAST architecture
Contractor: Methow Valley Builders 
CLT: Vaagen Timbers
Concrete subcontractor: JR’s Five Star Concrete
Geotechnical Engineering: GeoEngineers

See more here.

Hawthorne Hills Three:
Single-family residence, ADU & DADU

This project renovates an existing home and adds an attached accessory dwelling unit (AADU), and a detached accessory dwelling unit (DADU) to thoughtfully develop this single-family home into three rental units in the desirable Hawthorne Hills neighborhood of Seattle. It brings forward a model of urban density, providing much needed ‘missing middle’ housing. The exterior of the two buildings is unified in onyx-grey fiber cement siding with cedar accent areas. The home is 4-Star BuiltGreen certified.

The main home, with three bedrooms at 1,150SF, is renovated for modern living. The kitchen features three skylights that maximize natural light and brighten the core of the home. The original warm oak floors were refinished and unify the spaces.

The 410SF AADU takes advantage of the original house’s slightly set back position on the lot to build a new unit to the front and side setback.  The entry opens to the bright kitchen and living space. Within the compact footprint, a hallway through the utility room leads to the bathroom and a separate bedroom.

The backyard cottage is a 1000SF two-story home. Situated on the lot for privacy, a private walkway leads to the front door. The DADU boasts three bedrooms with vaulted ceilings on the top floor. Downstairs, a generous great room and kitchen with expansive glass doors open to the patio and private backyard. The efficient, open plan and bonus storage add to the versatility of the home.

See more here.

TEAM
Builder: Cadre  General Contractors
Civil: Davido Consulting Group/Watershed
Survey: Terrane
Structural Engineer: Owen Gould
GeoTechnical: Cobalt GeoSciences
Andersen Windows & Doors

Photography: Peter Bohler

New tribal Hatchery & Beach Shelter

At the beach at Point Julia on land occupied by the tribe since time immemorial, the Port Gamble S’Klallam Tribe’s Hatchery and Beach Shelter combines pragmatic uses with symbolic content. Salmon fishing is central to the Port Gamble S’Klallam Tribe’s traditional identity and its contemporary outlook. The new 1,800 SF two-story building accommodates both office and utility space for the Port Gamble S’Klallam Tribe’s salmon hatchery program, along with a separate open-air structure used by the Tribe’s commercial fishing operations. This project recognizes the cultural importance of both the place—a focal point of their history—and the program, while providing solutions to allow these activities to flourish in the 21st century.

The lower level of the Hatchery houses a garage, maintenance shop, and egg-incubation room with equipment that is both durable and moveable. The upper floor contains offices, water-quality testing, and filtration equipment. The conference room on the southwest corner can be entered separately, accessible to the wider community.

The new hatchery forms a gateway to the beach from the landward side, and the beach shelter is the Tribe’s front door on the sea. It will provide a work area for fishermen who pull their boats onto the beach and will also provide recreation space for the community. On the beach between the two structures, the native landscape is being restored, along with traditional edible and medicinal plants, and salt-tolerant erosion control plantings.

See more here.

TEAM
Owner: Port Gamble S’Klallam Tribe
Architecture: CAST architecture
Photography: Lara Swimmer
Contractor:  Pacific Civil & Infrastructure
Geo-tech: Robinson Noble
Structural: Swenson Say Faget
MEP: Glumac
Civil: Cannon
Landscape Architect: Pacific Landscape Architecture
Windows: Jeld-Wen  
Archeologist: Willamette Cultural Resources
Survey: AES Consultants
Intake System Engineer: Kleinschmidt Group
Specifications: Applied Building Information
Art/light installation: S’Klallam artist Jimmy Price
Conference table / Entry bench: Craig Kohring

An array of CAST’s detached accessory dwelling units (DADUs)

Statewide efforts to boost housing options make headway

This past legislative session, several bills made it through both houses and each will have long term benefits for the production of urban infill housing types such as cottages, ADUs, and small stacked apartment buildings.

HB 1337

The passing of HB 1337 expands housing options by easing barriers to the construction and use of ADUs.

·        legalizes two ADUs per lot in any configuration of attached/detached

·        legalizes an ADU on any lot size that’s legal for a house

·        legalizes ADU size up to at least 1,000 SF 

·        legalizes ADU height up to 24 feet

·        ends requirement for owner to live on site

·        caps impact fees at 50% of those charged on houses

·        lifts parking mandates within 1/2-mile or 15 minutes from transit stop

·        prohibits design standards or other restrictions more stringent than what applies to the main house 

·        legalizes ADUs to abutting property lines on alleys

·        legalizes ADUs in existing structures that violate current rules for setbacks or lot coverage

·        prohibits requirements for public right of way improvements

·        legalizes the sale of ADUs as condominiums

HB 1110

The Middle Housing Bill will mandate that medium and large cities create development standards for their lowest density zones to accommodate more housing.  For Seattle, it means:

·        Up to 4 units on any parcel not previously limited by an HOA or PUD.

·        Up to 6 units on parcels that are within ½ mile (a 10 minute walk) of frequent or fixed transit

·        Up to 6 units on any parcel if 2 are designated as affordable. 

The form that these new housing types will be open ended, but the Department of Commerce is busy developing a model code for cities to use as a starting point.  The deadline for cities to comply is 6 months after their next comprehensive plan cycle (for Seattle that is mid 2025). 

Spokane Four

As one of the region's leading voices for abundant and affordable housing choices, we have been advocating for backyard cottages—accessory dwelling units (ADUs)—since Seattle first considered them citywide in 2009.

More efficient land use is critical to address our housing crisis, climate change, and persistent inequities in access to housing opportunities. Modest infill houses like ADUs are a key strategy to empower citizens to provide new housing, build generational wealth, and leverage taxpayers’ investment in infrastructure, transit, schools, and parks.