Backyard Cottage, Seattle

Location: Seattle, WA

Size/cost: 800 sf / $89,760 (owner constructed, certificate of occupancy winter 2012)

Description: Approached by a start-up construction company, the clients wanted a Detached Accessory Dwelling Unit (DADU), or Backyard Cottage, designed in a modernist style and maximizing the city’s allowable area. Massaging every inch of the floor plan and height allowances, we achieved a comfortable two bedroom, two bath, and plenty of vaulted living space with views to Mt. Rainier, the Cascade and Olympic Mountains.

The clients expressed careful consideration of the neighbor’s privacy and impact from the new Backyard Cottage. Views from the Backyard Cottage respect neighbor privacy by being directed through view corridors elsewhere and a cedar slotted partial height wall screens the entry to the Backyard Cottage from the neighbor’s home. Aluminum channeled stucco and stone veneer, open reveal fiber cement board, minimalist glass balcony rails, and simple detailing throughout comprise a sleek and linear exterior, while the same stone veneer, bookmatched cabinetry, painted white gypsum light shelves, hardwood floors, polished concrete, and high-voltage light fixtures continue the modernist expression on the interior. Ample expanses of glass bring the outside-in and establish a connection to the outside world while making the interior rooms feel more spacious. Where normally an extended overhang would suffice, a motorized exterior shade controlled via remote from inside will provide respite from intense summer sun due to height regulations (in an effort to keep structures within a non-obtrusive neighborhood scale).

Sustainable features of the Backyard Cottage include an augmented thermal envelope with minimal thermal bridging, energy-efficient heating, lighting, plumbing, high-performance [operable] windows, Insulated Concrete Forms (ICFs) foundation system, fly-ash concrete, long-lasting durable finishes, ductless through-wall fresh air ventilation, and solar screening allowing for passive acceptance of low winter angle sun while blocking high angle summer sun.

High R-value rigid insulation surrounds the structure and a rain screen air cavity between the weather barrier and siding materials extend the life of the Backyard Cottage shell– the most expensive walls to repair in standard homes. Embracing the Passive Haus paradigm shift currently taking place in the architecture world, investing in improving the thermal envelope allows for reduction of mechanical heating systems initially and in the long-term future. The in-floor radiant heat is comprised of a closed-loop glycol-water mixture that is heated by piggy-backing off the on-demand domestic hot water heater, eliminating the need for a dedicated boiler.

Currently under permitting review by the city, the clients are beginning the construction of ornament concrete planters and water features that help meld a modernist transition from the existing residence to the Backyard Cottage.

The clients were able to do a virtual walk-through and fly-over of the project to ensure their vision was being met and to address any concerns prior to going-in for permitting.