Castle House California home, Modern Hillsborough real estate, USA residential architecture photos
Castle House in Hillsborough, CA
August 8, 2025
Architects: Koami Architecture
Location: Hillsborough is an incorporated town in San Mateo County, California, United States, in the San Francisco Bay Area, USA
Photos by Maige Studio
Castle House, Hillsborough, San Mateo, California, USA
Castle is a single-family home in a quiet residential neighborhood of varying typology in Hillsborough. To respect the quaint character of the street, we proposed horizontal expansion below the existing roof ridge farther away from the street.
On the side not visible from the street, a modern design language with flat roofs with an open concept is introduced; a new rectangular form is juxtaposed against the California ranch-style home, and one big gesture of a horizontal line ties everything together cohesively.
This line creates the design datum, provides shade and weather protection for outdoor space, and finally becomes a roof allowing the building volumes to step down along the site’s natural sloped topography gradually.
The primary bathroom is a place of rejuvenation inspired by the Japanese outdoor onsen bathing custom that borrows the outdoor natural elements as part of the serene bathing experience.
how does the design of Castle balance the traditional California ranch-style with modern architetural elements, and what inspired this unique juxtaposition?
The design of Castle strikes a careful balance between the timeless appeal of the traditional California ranch-style and the clean simplicity of modern architecture. By preserving the low-slung horizontal form and welcoming front façade typical of ranch homes, while introducing minimalist detailing, refined material transitions, and open spatial flow, the design feels both grounded and current. Inspiration came from the clients’ desire for a home that honors California’s architectural heritage while supporting a modern lifestyle centered on indoor-outdoor living, natural light, and a sense of calm.
Castle House, Hillsborough, California – Building Information
Architects: Koami Architecture – https://www.koamiarchitecture.com/
Photography: Maige Studio
Castle House, Hillsborough, California, USA images / information received 080825
Location: Hillsborough, California, USA
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