Accessory Dwelling Units (ADUs) and Detached Accessory Dwelling Units (DADUs) are transforming the housing landscape in urban areas. These self-contained small homes, can be attached or stand-alone and are becoming increasingly popular in cities grappling with housing shortages, rising costs, and shifting lifestyle preferences.

Help Housing Shortages
The surge in demand for housing has put significant pressure on urban neighborhoods, where space is limited and housing affordability is a critical issue. ADUs and DADUs offer a practical solution by increasing the housing stock within existing neighborhoods.

Affordability + Flexibility
ADUs and DADUs provide an affordable alternative for renters and homeowners alike. Homeowners can use these units as rental properties, offering housing at a lower cost than traditional apartment units. They can also serve as multi-generational living spaces, allowing families to stay connected while maintaining privacy. For many, ADUs are a way to downsize without leaving their neighborhoods, contributing to economic diversity in communities.

Ease Zoning Regulations
Cities across the US are revising zoning laws to encourage the construction of ADUs and DADUs. These policy changes make it easier for homeowners to build these units by reducing permitting costs, relaxing parking requirements, and increasing maximum allowable sizes. In Seattle, for example, pre-approved DADU plans streamline the process, saving time and money for homeowners.

Sustainability
These small homes align with urban densification goals. By utilizing existing infrastructure and minimizing the need for new developments these homes help reduce urban sprawl. Additionally, their smaller size typically results in lower energy consumption.

Enhance Community Character
Thoughtfully designed DADUs can blend seamlessly into existing architectural styles, adding diversity to the housing stock while preserving the integrity of the neighborhood.

See more: www.castarchitecture.com/backyard-cottages-new

Matt Hutchins addresses the critical issue of “missing middle” housing in the U.S., exploring the housing gap that falls between single-family homes and high-density apartments. Serving as a jury member for the Denver Single-Stair Housing Challenge organized by Buildner, he focuses on innovative solutions to promote accessible, medium-density housing options.

Watch on YouTube: https://www.youtube.com/watch?v=orW8tnmPSv0

Missing-middle housing is a housing type that fits in the middle between single-family detached houses and larger apartment buildings. That’s duplexes, tri-plexes, four-plexes, ten-plexes, and small apartment buildings. It’s any sort of increment of density that is greater than a single-family house, but isn’t the blocks of apartment buildings that is much of what we see in the development world today. Missing-middle housing is important for urban development because American cities have lots of space. They are nowhere near full. We have empty parking lots. We have lots that were never developed. We have space in our cities we can use or reuse. There are many opportunities within our cities to densify and make use of existing infrastructure without having to assemble a whole block or use more “high-wire acts” with regard to development.

• Make good use of small lots

• Use of single-stair buildings is a critical tactic for taking advantage of small urban lots

• Adapt building regulations and make required changes

• Use underutilized urban land

• Use space correctly

• We have already invested in the urban infrastructure

• We can have a more efficient city and residents with a lower carbon footprint

• ADUs and DADUs are powerful tools to keep communities together, keep the property in family, and create generational wealth

• Missing-middle housing is compact, efficient, and sustainable

The Kirkland Cedar Cottage shines. It has an extremely efficient footprint that provides well daylit living space, necessary storage, flexibility, and a covered outdoor living area.

Bathed in natural light, a generous central area includes the kitchen, dining, and living spaces. The cottage is accessible with one-level living, flush entry thresholds and flooring transitions, a galley kitchen, and a generous entry that connects the spaces. 

Carefully placed large windows and glass entry doors flood the area with light that bounces off the white walls to make it feel larger than its square footage. The open glass doors and deep eaves create a vibrant indoor/outdoor living experience.

Square feet: 467

Green Design: Energy-efficient heating, cooling, and water heating systems, passive solar heat gain in window/shading, all LED lighting, low VOC recycled and renewable materials, and no fossil fuel use appliances.

Interior Designer: Jayne Douglas Design
Builder: NW Finishing
Photos: Kara Mercer

This cottage was recently featured in Kirkland Lifestyle.

Read the Article Online Here (Page 22-23)

View a PDF of the Article Here

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

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

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

Beacon Hill Cedar Cottage is one of CAST’s City of Seattle Pre-approved cottage plans

Designed by CAST and built by the homeowner who is also a contractor, Beacon Hill Cedar Cottage includes the amenities and feel of a larger home. Its efficient footprint provides two bedrooms, well-daylit spaces, lots of storage, and a covered outdoor living area.

Bathed in sunlight, a generous central area includes the kitchen, dining, and living spaces. Carefully placed large windows and glass entry doors flood the area with light that bounces off the white walls to make it feel larger than its square footage. The open glass doors and deep eaves create a vibrant indoor/outdoor living experience.

The durable Japanese cypress exterior is treated using the traditional Shou Sugi Ban technique, ensuring both beauty and natural resilience.

With two bedrooms, and maximized storage throughout, there is plenty of room to keep things close at hand to pursue hobbies and work from home.

Square Feet: 707 + 147 SF patio

Photos: Peter Bohler Photography + Director
Shou Sugi Ban exterior: Nakamoto Forestry
Windows: Marvin  

See More: Beacon Hill Cedar Cottage

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. 

Seattle architect talks about the BENEFITS OF LIVING IN A TINY HOME

CAST is featured in ISN’s article: Tiny Home vs. Traditional Home: What You Need to Know

Tiny homes and small space living offer a bevy of rewards to those who decide they don’t need many things and are ready to streamline their life. There are many reasons to choose small space living. Some people may want a house that moves with them, to not have a mortgage, or simply to live lightly. 

Lower Energy Usage

Tiny homes consume less energy and cost less to maintain. Smaller appliances are typically more efficient. One will use less energy, and water, and create less waste. A tiny home could potentially be heated with a wood stove and powered by a solar array. 

It Costs Less 

Tiny homes cost a fraction of the price of traditional homes. The cost to own or rent will be significantly less and they cost less to maintain. Since small spaces use less energy, there will be less outlay on all bills related to the home. Reducing housing expenses may let owners/tenants save money for (or in) retirement, travel, or allow them to decide to work less.

Streamlined Maintenance

A tiny home is easier to maintain. With fewer appliances to repair, less exterior area to maintain and even less space to clean, those who live in small spaces may have more time to spend on work, fun hobbies, and their relationships.

Mobility

Tiny Homes can be made to be mobile. Whether it’s a vacation or a new permanent spot, a tiny home can be built to travel.

Minimalist lifestyle

De-clutter. There is only room for the important things and those things that matter most. Plus, there is also the opportunity for more focus and less distraction. A tiny home can be constructed from recycled, repurposed, and salvaged items.

Eco-friendly living lifestyle

By using less energy tiny homeowners reduce their carbon footprint. There is only room for vital appliances, so you save on electricity bills. Also, there is the potential for minimal expense on a rainwater collection system and composting toilet. The tiny home can be designed to be completely off-grid.

Photos by: Cindy Apple Photography