Experimental Steel House Known as The Eichler X-100 Lists for $4.5 Million
The circa-1956 Northern California property, which is on the National Register of Historic Places, was an experiment in homebuilding
For the first time since 2013, a mid-century modern experimental steel house known as the Eichler X-100 is on the market with an asking price of $4.498 million. Built in 1956 by Eichler Homes and designed by Jones & Emmons, the historic property is part of the San Mateo Highlands Eichler Homes development in San Mateo, California.
Real estate developer Joseph Eichler founded Eichler Homes and made sure that each of these dwellings would be modernist and designed by architects. The company’s specialization was crafting affordable wood-framed houses, typically made of timber, as opposed to the more standard tract homes. And because the home was experimental, it was used as a laboratory for Eichler’s designs, materials, and products.
“There are Eichlers, and then there is the X-100,” listing agent Eric Boyenga of the Boyenga Team at Compass tells Galerie. “This wasn’t another model in a neighborhood—it was a full-scale experiment in what a home could become. To me, that is what makes it the greatest Eichler of them all: it didn’t just express Eichler’s vision—it pushed it further.”
In Eichler’s mind, the X-100 was a sort of vessel to raise awareness about steel-framed housing and potentially “revolutionize residential construction,” according to the home’s website. Two additional reasons he commissioned the X-100 were “to showcase advanced household appliances, some of them prototypes; and to promote his in-progress San Mateo Highlands development, whose location was, at the time, remote from highways.”
In total, the Eichler X-100 boasts three bedrooms and two living rooms, along with two interior gardens, a child-friendly yard, a swimming pool, and scenic views of the Santa Cruz Mountains. And while it’s not confirmed why the home is called the X-100, it’s been theorized that it came from the X-15, a hypersonic rocket-powered aircraft constructed in the 1950s.
Originally, the steel house’s interior was designed by Knorr and Associates, with furniture by Herman Miller and accessories by Gump’s. There is still a conical-shaped fireplace in the entry garden; it used to rotate but is now stationary. Also remaining is a metal star sculpture—on the front exterior of the home—by artist Matt Kahn, who worked as an interior design consultant for Eichler Homes. The total cost to build the home was $125,000.
In 2003, a group known as the X-100 Partners purchased the property. Since 2013, one of those partners, Marty Arbunich, who is also the director of the Eichler Network, has been the sole owner.
“I owned and managed the Eichler Network and CA-Modern Magazine for the past three decades. Passing the torch of X-100 ownership has been part of my overall retirement plan since the early 2000s. When I finally retired in January 2026, I put the proverbial ball into motion, and here we are today, at the front door of the X-100’s next owner. It’s a sad day, but nonetheless right on schedule,” Arbunich tells Galerie.
He adds, “I’ve been a huge fan of the X-100 since the mid-1990s, when I began to assist then-owner Anna-Lise Pedersen [who lived here for 40 years] with vendors to help keep the house in tip-top shape. Anna-Lise, whose spirit seems to still radiate throughout the X-100’s interior, loved the X-100 dearly, was a wonderful caretaker, and was a great inspiration for me. When she passed in 2003, I knew it was time for me to jump into action, and continue to oversee and preserve the home, which I did faithfully for the next 23 years. And I’m so glad I did.”