SAW Transforms a Hillside Home in Mill Valley, Opening and Expanding its Core

The project, known as The Middle Half, dramatically reconfigures the home’s core to create an open, light-flooded interior and direct connection to the landscape. Raw, textured materials like galvanized steel, rough-sawn cedar siding, and cast-in-place concrete define the project and accentuate its unexpected, layered geometries.
San Francisco-based Spiegel Aihara Workshop (SAW) has completed the transformative architectural and landscape design of a 1962 home in Mill Valley for a couple and their two young children.

“Often when thinking about preserving a thing—a structure, an object, a landscape, a city—one talks about preserving its ‘heart’ or its ‘core.’ But in this case it was the opposite—we were trying to preserve the periphery, while completely reimagining the core,” says SAW co-principal Dan Spiegel.

©Mikiko Kikuyama

The original 2,746-sf mid-century home featured a segmented layout of small rooms and a highly congested core. While the homeowners were fond of its modest horizontal facade and straightforward approach to materials, they recognized the effects of aging and organizational flaws, which bifurcated family living patterns and severed the interior from the site’s views. SAW’s design enlarges the home to 3,457-sf, unlocks its layout to create an open-plan central living space, and enhances its connection to the dramatic vistas. Throughout the home’s interior, fixtures and finishes were designed collaboratively by SAW and one of the homeowners, Kina Ingersoll of Kina Ingersoll Design Workshop. Ingersoll also selected all of the furniture.

The design is defined by a sense of expansion as one moves from the front of the house, which is one level along the street, to the back of the house, which carves down to two levels and faces a steep, lush valley. “It’s meant to be perceivedas a building that is both low and extremely high,” says Spiegel.

©Mikiko Kikuyama

Approaching from the street, the facade is low-slung and grounded in the landscape. Lateral rough-sawn Western Red cedar cladding enhances its horizontality, while slatted trellises slip beyond the roof and frame the front entrances against the guiding angled wall of the garage. A feeling of suspension quickly takes over upon entering the home, where a new circulation path crosses through the diffuse core, drawing a clear slightline from the front door to the suspended rear deck and views beyond. “A basic premise of the design is to use a landscape gesture—a corridor between the front yard and the valley views—to resolve the tension between building elements,” says SAW co-principal Megumi Aihara.

This path connects the home’s communal spaces (kitchen, dining area, living room, family room, and outdoor deck) along a central axis, while more private areas (bedrooms, bathrooms, office, and guest suite) peel off to the left and right. Through the front door, a tall, narrow entry corridor opens quickly into a wide, open-format kitchen and dining area beneath exposed-beam ceilings, which are perforated by skylights that punch up and seem to peel back portions of the roof. Crisp white gypsum walls and floor-to-ceiling white millwork enhance a sense of buoyancy and lightness, as subtle long-stemmed pendant lights suspend over a minimal gray kitchen bar volume and a live-edge dining room table, designed by one of the homeowners.

While the entire home is an exercise in blurring distinctions between interior and exterior, this reaches its fullest expression at the rear. The kitchen-dining zone spills without interruption into living and family rooms bordered by floor-to-ceiling windows and glass doors that open to the suspended upper deck, implying layered continuity. The sensation is enhanced by interior ceiling beams that extend into outdoor space, forming a slatted trellis over the back deck. “The steel frame is continuous, defining the space of inhabitation across thresholds,” says Spiegel. “It carves volume out of the air, claiming territory even on the exterior, even without enclosure.”

©Mikiko Kikuyama

SAW’s design ensures that even the home’s more intimate rooms converge with the landscape. A new, expansive 16-foot-wide sliding door carves into the primary bedroom’s front wall. This opens onto the redesigned front garden, planted with a lush array of azaleas, lilies, and grasses. The connected primary bathroom is likewise organized around a window that reveals the front yard’s camphor tree.

The client’s approach to the interiors also melded indoors and outdoors. “What inspired me was my upbringing in Hawaii and the constant connection to nature you have growing up there….I wanted our house to exhibit all of these inspirations: a connection to nature (with large back doors opening to our yard and the surrounding woodland surroundings), and an interior that exhibited a subtle mix of cultures, from old world to new world, Eastern to Western, and modern to traditional. One example of this thinking was our dining room table. We sourced the slab of black walnut from an east coast lumber company on Etsy and then we hired a local woodworker to finish it and a local metalworker to build the raw steel legs that I designed.”

©Mikiko Kikuyama

Extending from the right of the kitchen-dining area, a short hallway stitches the main volume of the home to the kids’ wing, which angles to the west. Windows lining this threshold, create a visual connection through the volumes, revealing the home’s layered, slipping geometries. On the other side of the kitchen, a stairwell slides subtly behind the family room’s open bookshelf down into a lower level bar/lounge, guest room, and office; previously, there had been no interior connection between the upstairs and downstairs. The lounge also features glass floor-to-ceiling sliding doors that open onto the lower deck.

SAW designed the rear landscape to be volumetric, defined by geometries shared with the architectural design. The wide upper deck connects to the stepped lower decks with a sharply defined, hefty cedar staircase and railing made from galvanized steel posts and stainless steel cable. The pool, located on the lowest deck, is seamless at one side—a void in the landscape—and yet a solid rectilinear block in the hillside from another. Below, terraces stagger as “landscape rooms” across the slope.

“The most critical building elements—the steel and wood beams and columns—break free of the constraints of the interior walls to carve out and define volumes of exterior space, framing views as pictorial scenes,” says Aihara of the connection between architectural and landscape design across the project.

©Mikiko Kikuyama

Other images can be seen in the gallery down below

Project Data:
Architecture & Landscape Architecture: SAW
General Contractor: Perfection Construction
Structural Engineer: GFDS
Civil Engineer: Benjamini Associates
Millwork: Marco Hernandez Custom Cabinetry
Geotechnical Engineer: Nersi Hemati
Interior Design: Kina Ingersoll of Kina Ingersoll Design Workshop

SAW is a transdisciplinary design firm, operating at the nexus of architecture, landscape, and urban design.

This mix allows us to work across scales (from the tactile object to the city) and timelines (from the immediate to the ecological) at the onset of a project. We work to identify the blind spots between disciplines and take advantage of the hidden opportunities therein. We believe in the transformative power of good design, in the inextricable relationship between building and context, and in the vital role the built environment plays in the development of community. We view design as a collaborative, research based process, and work closely with clients to better understand their needs and advance their goals.

Dan Spiegel, AIA
Founding Partner, Principal
Dan received a Master of Architecture from the Harvard University Graduate School of Design and B.A. in Public Policy from Stanford University. Prior to founding SAW, Dan worked for a number of leading architecture offices in New York, Beijing, and Boston. He currently teaches architecture at UC Berkeley and California College of the Arts (CCA) and has been an invited design critic at several schools of architecture, including Harvard University, Rhode Island School of Design, and California College of the Arts. Dan is a licensed architect in the states of California and Hawaii.

Megumi Aihara, ASLA, PLA
Founding Partner, Principal
Megumi has ten years of professional experience creating landscapes, big and small. Prior to joining SAW, Megumi was a Senior Project Manager at Michael Van Valkenburgh Associates, and a Landscape Architect with Andrea Cochran Landscape Architecture. Megumi received a Master of Landscape Architecture from the Harvard University Graduate School of Design and a B.A. in Visual Arts from Brown University. She is an Adjunct Professor of architecture at California College of the Arts (CCA). Megumi is a licensed Landscape Architect in the states of California and Hawaii.

Jeremy Ferguson, Associate
Jeremy received his Master of Architecture from the University of California at Berkeley where he was the recipient of The Mario Ciampi Art in Architecture Award demonstrating outstanding artistic merit. Originally from Hawai’i, he received his his Bachelor of Arts in Environmental Design from the University of Hawai’i at Manoa before moving to the Bay Area. His other professional experience includes positions at MODEM in Oakland, Randolph Designs in San Francisco, Dean Sakamoto Architects in Honolulu, and the National Disaster Preparedness Training Center at the University of Hawai’i.

Sharon Ling, Associate
Sharon received a Louisiana ASLA student honor award in 2015 before earning her Masters in Landscape Architecture from Louisiana State University. Originally from China, Sharon holds a Bachelor degree of Landscape Architecture from Nanjin Forestry University.

Namhi Kwun
Namhi received the San Francisco CSI Foundation award in 2017 before earning her Bachelor of Architecture degree from the California College of the Arts. Her other professional experience includes positions at Urban Works Agency, Mark Cavagnero Associates in San Francisco, and The Plus Architect in Korea.

Avery Sell Avery is a landscape designer educated at the Pennsylvania State University Stuckeman School of Architecture and Landscape Architecture where he received an ASLA Student Honor Award and was named the 2014 Student Marshall. He brings to every project ideas that blend the mundane and the extraordinary, social science and sustainability, and past and future histories. Prior to moving to San Francisco, Avery worked in Philadelphia as a creative consultant, an artist’s assistant, and as a project manager at David Rubin Land Collective.

Shinji Miyajima Shinji is an international designer from Japan and received his Master of Architecture from Rice University and Bachelor of Science in Architecture from the University of Cincinnati. Prior to joining SAW in January 2021, he worked at architecture and architectural lighting design offices in New York, San Francisco, Los Angeles, Dallas and Houston.

Tiffany Xu
Tiffany Xu is an architectural designer. She earned her Master of Architecture from Rice University where she was Co-Editor-in-Chief of PLAT Journal and recipient of the William D. Darden Thesis Award. She completed a B.A. in Natural Resource Conservation and Art History from University of California, Berkeley. Prior to joining SAW she worked at the offices of Jim Jennings Architecture, Sidell Pakravan, and Mollet Geiser & Co.