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Even from a distance, there was something distinctly different about the accessory dwelling unit being built by Hollister’s DH Construction on a local property. There was no sign of the usual plywood being used to frame the exterior and interior walls. In its place was a dull gray stone-like material that has been setting the standard for residential fire safety.
These panels, manufactured by ZS2 Technologies, are produced from a type of magnesium oxysulfate cement that has withstood furnace tests of over 1,600 degrees Fahrenheit, 500 degrees greater than the flashover point at which everything in a room would ignite.
In a real-world example, according to ZS2 Vice President of Business Development Shil Patel, a $3 million home in Canada built with the panels was caught in a forest fire and sustained only $50,000 in damage—mostly from smoke exposure.
“Essentially,” said DH Construction owner Darin Hopkins, “this material will save your life. If a fire breaks through and there’s nowhere to go, these walls are not going to ignite, and the house is not going to catch on fire.”
The technology is not new—Hopkins said a version of the cement was used in building the Great Wall of China—but its application in housing has steadily increased over the last 20 years. Hopkins said he first became aware of the technology four years ago, when he met Patel and became fascinated with the panels and their potential to revolutionize the way homes are built.
“I was looking at the future,” Hopkins said. “Construction’s been the same for 100 years. It’s about time something changed. These guys clearly figured it out. These panels are just unbelievable.”
Patel said that the formulation of the cement used in the panels was created by four on-staff chemists using magnesium sequestered from waste, and was intended to address the needs of climate change. They are meant, he said, to be deployed to what he called “climate active zones” threatened by fires, hurricanes, tornadoes and flooding.
“These zones are becoming more predominant in the U.S. and the Canadian markets,” he said. “They tend not to qualify for insurance or use building products that are going to withstand these climate events.”
Hopkins became a strategic ZS2 TechPartner partner in 2021 and, with his son Daniel, formed Advanced Building Technology to broker the panels to other builders in California.
“Showing this to new crews is always amazingly fun,” Daniel said. “Their eyes light up. They all like it because it’s new and out of the norm. And they understand the resilient part of it and overall how much more beneficial it is to build with this.”
Construction of ADU. Courtesy of Darin Hopkins. 
Construction of ADU. Courtesy of Darin Hopkins.. 
ADU construction project. Photo by Robert Eliason. 
Keyed wall panels at ADU site. Photo by Robert Eliason. 
Magnesium oxysulfate cement. Photo by Robert Eliason. 
Daniel and Darin Hopkins at ADU site. Photo by Robert Eliason.
Darin said the half-inch-thick panels offer more qualities than just being fire resistant. Unlike standard plywood sheets, he said, when properly sealed, they resist termites and other insects, dry rot, water, bacteria, mold and rodents. Thicker panels can also be used as subflooring or roofing.
The panels are also strong, Darin said. More than 250 pounds can be held by a single screw without drilling into a stud. And they are “dead straight,” he said, which ensures precise window openings and eliminates issues like baseboards separating from the wall or floor due to uneven studs.
Finished panels for use in construction are a minimum of 6.5 inches thick and consist of two sheets of magnesium oxysulfate cement sandwiching thick foam insulation. Certain panels may also contain conduit for electrical wires.
Daniel said each panel is custom-designed, following architectural plans, making the eventual placement of the walls “like putting together Legos.” All window and door cutouts for the exterior walls, he said, are made in the panels, so there’s no need for on-site cutting.
Daniel said that the modular nature of the panels significantly speeds up construction time. For example, he said, a recently built 3,200-square-foot house had its exterior walls put up in just two and a half days with a crew of six, cutting the usual time nearly in half.
While the price of the panels is slightly higher than plywood, Darin said, the cost benefits may make it cheaper to use in the long run, as illustrated by a current project in Calaveras County, including107 affordable homes being built for Habitat for Humanity.
“They live at the base of the Sierras,” he said, “so they are looking at the big picture. It is costing them a little bit more, but think about what you’re going to get in the long run.”
And, as homes constructed with the panels become more widespread, he sees a chance they will be adopted as a standard throughout the state.
“It’s going to take some time,” he said, “but I can see this being a requirement in new construction in California. Definitely in rural areas, but why wouldn’t you want it in the city? It’s exciting watching this come together.”
ABC 10 report on the Angels Camp project in Calaveras County
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