International studio Mork-Ulnes Architects has created an angled accessory dwelling unit in the mountains of Marin County, California with wooden interiors and a loft space.

Completed in the spring of 2023, the Crest Guesthouse measures 411 square feet (38 square metres) and was built on the old foundations of a former garage by Mork-Ulnes Architects, which has offices in San Francisco and Oslo, Norway.

"The building's sharply angled roofline mirrors the slope of the site and gives a high clerestory window light above the cabinetry wall, while a playful flip in the roof provides a punched window from the loft viewing the trees," the studio said.

Accessed from a northside driveway that slopes down to the primary residence, the house is balanced on the steep slope and uses a longitudinal wooden deck on the east side of the house to double the usable area and take advantage of the mild California climate.

The compact dwelling is clad in light grey Cembrit fibre cement panels, selected as an easy-to-maintain, fire-resistant cladding in the densely wooded setting.

Light comes in through sliding floor-to-ceiling glass doors with metal frames and a small square window in the loft, both of which look down the hillside to the east, and clerestory plate glass windows on the western hillside.

Currently serving as a temporary residence while the main house is being renovated, the ADU was built as a small guesthouse and a rental unit — following the footprints of the former garage, but utilizing a flexible program to maximize the area.

Inside the primary room is wrapped in Douglas Fir veneer plywood for a smooth, natural-toned, multi-use space.

The Murphy bed folds up into the wall during the day and the kitchen island can be rolled into place when needed.

The compact kitchen with square white tile backsplash and Caesarstone counters runs along the western wall and a small seating space with a padded green bench is tuned into the millwork that creates the closet.

Small nooks like a triangular cubby under the roofline and a square portal into the loft break the planes of the interior walls.

Other than white globe lights and a television set on the wall, the space is mostly unadorned, leaving the view to be the decoration.

The bathroom is split into two smaller rooms with the toilet and sink tucked into the corner of the house.

Meanwhile, the shower room, tiled entirely in forest-green Daltile Keystones, serves as a pass-through to the exterior with a frosted glass door. The inside of the interior door is mirrored to bounce light around the small space and is accented by chrome fixtures.

The loft space, which is accessed through a narrow ladder tucked behind the kitchen wall and an exterior staircase, is a small reading nook or could be used as a temporary sleeping space.

In addition to the ADU, Mork-Ulnes recently completed a gabled home clad in black-stained cedar in San Francisco and an eight-sided residence made of cross-laminated timber in Bend, Oregon.

The photography is by Bruce Damonte.

Project credits:

Project design team: Casper Mork-Ulnes, Phi Van Phan, Robert Scott, Lexie Mork-Ulnes, Kaoru Lovett
Job captain: Kaoru Lovett
Engineering structural: David Strandberg
Civil: Adobe Associates, Inc. (Aaron R. Smith)
General contractor: Damner Construction Axelson Builders
Communications partner and press office: The Architecture Curator