The X-100’s Three Design Ideas: Steel Structure, Interior Gardens and a Central Service Core

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

The X-100 is especially useful to study because its open interior was designed through several connected choices. Steel structure, interior planting and a central group of service rooms work together to organize the house.

Calling it an open-plan home is accurate but incomplete. The more interesting question is what makes that openness possible, and how the plan preserves a sense of organization without relying on a conventional sequence of enclosed rooms.

A steel frame separated support from interior partitions

The National Register nomination identifies the X-100 as a 1956 Eichler Homes experimental residence designed by Jones & Emmons with structural engineer William R. Mason. It describes exposed steel posts and beams and interior walls that do not carry the structure.

That distinction is fundamental to reading the plan. The elements that support the roof are not required to coincide with every boundary between activities. Structure and room division can therefore be considered separately.

For a visitor looking at a drawing, the first useful step is to find the supporting framework. Once that is understood, the openness becomes a deliberate architectural arrangement rather than simply the absence of walls.

The central core gives movement a clear pattern

The nomination describes a concentrated core containing bathrooms, utility space and kitchen functions. Circulation moves around it between bedrooms and living areas.

A central core can organize an otherwise broad interior. It provides something to move around, gives related services a common location and creates distinct routes without requiring a corridor to divide every part of the house.

This is a useful distinction when comparing floor plans. A plan can be open and still have a strong center. Openness does not have to mean that every activity occupies an undifferentiated rectangle.

Two planted interiors bring landscape into the plan

The historic record identifies two internal garden areas lit from above, one near the entrance and another near the bedroom side. Circular concrete paving and planted gaps connect the landscape vocabulary inside and outside.

These spaces change the relationship between a room and a garden. Instead of placing all planting beyond an exterior wall, the plan gives landscape a position within the house’s organization.

The result can be read in section as well as in plan. Light arriving from above has a different relationship with a space from light arriving only through a perimeter wall. The gardens consequently participate in how the interior is illuminated and perceived.

The rear glass wall emphasizes a different boundary

The nomination describes the broad western living area opening toward a rear wall of glazing. This is part of the house’s documented historical design, rather than a new inspection of its present condition.

The contrast with the central core is instructive. The core provides concentration and organization; the glass edge directs attention outward. Both are needed to understand why the plan feels expansive while retaining a recognizable structure.

For buyers interested in modern homes, the lesson is to examine relationships rather than collect features. A skylight, garden court or exposed beam can be attractive individually, but its architectural value often comes from how it works with the rest of the plan.

A particular experiment within a broader residential area

The X-100 should be understood as a specific experimental design, rather than assumed to represent the construction of every Eichler house. Its steel frame is central to that distinction.

Our San Mateo housing settings guide provides wider local context. Explore real estate and home for sale in San Mateo, and contact Diamond to compare homes with attention to how structure, daylight and outdoor space contribute to the actual plan.

Source checked October 28, 2026. This analysis uses the historic nomination; it makes no assertion about current sale status, availability for tours or approval of changes to another home.