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Private Sonoma Spa & Observatory

Architect / Firm: STUDIOS Architecture

Awards:    Year:    Entry Categories:

Awards:    Year:    Entry Categories:

STUDIOS Architecture

Contact Person

Darryl Roberson

Architectural Firm


Cello and Maudru Construction Company

Project Location: Sonoma, California
Owner: Confidential
Completion Date: 2007

This serene and beautiful private Zen spa and astronomical observatory provides its owners with both a tranquil retreat and stunning views of the night sky.  The project features a 4,000 sf concrete, stone and glass spa with a bath suite, home theater and lounge, and a 600 sf corten steel observatory.

The design is at once modern and rustic; clean lines and polished stone are juxtaposed with rough edges and rusted metal.  While the monumental custom fireplace and the bath suite are literally carved out of stone blocks, the lounge and home theater area is primarily glass and wood, providing an uninterrupted visual connection to the surrounding open landscape.  Exterior columns are interspersed seemingly at random, simulating the trunks of the nearby trees.  The large “floating” post-tension concrete roof allows for high ceilings and unobstructed views within the theater area.  The observatory’s pyramid form is reminiscent of an ancient Mayan ruin, echoing the owners’ extensive collection of native stone carvings and tapestries.

The observatory sits within a reflecting pool and is axially sited between an allée of ancient olive trees. Images from the robotically controlled 20-inch telescope, the Hubble catalog and other sources are displayed on a large rear projection screen in the home theater; a key project goal was to provide local schools and organizations with remote access to the telescope.

Located on a gently sloping lot, the site of the spa and observatory was carefully selected in order not to disturb the numerous old growth trees—including live oaks, bay laurels and buckeyes—that create an entry sequence from the main house.  The landscape has been replanted with drought-resistant native grasses in an effort to foster indigenous wildlife.  Dozens of ancient olive trees were reclaimed and relocated from a site slated for redevelopment; the olives will be used to make organic olive oil for commercial distribution.  Permitted for agricultural purposes, the property also includes an organic fruit and vegetable farm.

Design innovation and sustainability were key in this project. The team selected highly durable primary materials—concrete, limestone, weathering steel, and ipé wood—and low VOC materials and finishes were used throughout the interiors. Landscape walls and a pyramid sculpture were created using stones found on site.  All fixtures feature low-flow valves to increase water efficiency.  The low-volume underfloor air distribution system and radiant in-floor heating reduce noise levels and improve indoor air quality.

Energy optimization is achieved through several integrated approaches.  The spa facility’s foundation incorporates a large thermal mass mat that works in tandem with the underfloor air distribution to reduce cooling loads. When in use, the nearby lap pool serves as a secondary heating source for the radiant-heated floors.  Roof overhangs, sun shading and a custom-designed corten steel window framing system protect the large south-facing façade; triple-glazed insulated glass units reduce heat loss and solar heat gain while still allowing for ample daylighting.  All windows are fitted with integrated electronically controlled shading devices to further reduce solar heat gain and glare.

Andrea Cochran Landscape Architecture
STUDIOS Architecture

Holmes Culley | Structural Engineer
Flack + Kurtz | MEP Engineer
Summit Engineering, Inc. | Civil Engineer

Architecture & Light | Lighting Consultant
Charles M Salter Associates | Acoustics & AV

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