How They Pulled It Off: Retrofitting a Home Against Wildfire

Welcome to How They Pulled It Off, where we take a close look at one particularly challenging aspect of a home design and get the nitty-gritty details about how it became a reality.

In the 1980s, when he was in his mid-twenties, architect Lorcan O’Herlihy built a house for his parents on Trancas Canyon Road in Malibu. "It was really nice to give them a home back in ’87 that they really loved, and they were there for over twenty years," says O’Herlihy. Decades later, years after his mom had sold the home, he got a call from the new owners: It had burned to the ground in Malibu’s 2018 Woolsey fires, and they hoped he might return to the site to rebuild with his firm, LOHA. And so began what he calls Trancas 2.0—only this time, the house would be made from concrete, to make it as fire resistant as possible.

"I like to say we rebuilt a new home out of the ashes out of the previous house," says O’Herlihy.

The original house was made of plaster, itself a relatively noncombustible material in comparison to wood. But it did have a conventional roof (i.e., one with wood framing) that was no match for the flying hot embers generated by a strong wildfire. So this time, they settled on the idea of a "concrete defense system": a concrete roof without eaves, as well as concrete walls, floors, and slab. The exterior is effectively a bunker specifically built to withstand fire. Once O’Herlihy and the clients decided on concrete, that simple fact drove the rest of the decisions. "We said, okay, how do we celebrate this wonderful, tactile, interesting house out of concrete?" he says.

Their choice of material wasn’t the only constraint. The Malibu Building Council would allow an expedited permitting process—but only if they kept the footprint to within 10 percent of the original building. Plus, the owners liked the flow of the original house, with the living room and kitchen positioned to take full advantage of ocean views. At the same time, O’Herlihy saw an opportunity to elevate his original design.

"We were in a sense keeping with the existing [house]," he says, "but we were free to reinterpret, probing the possibility of space, light, and materiality. And that’s what really drives the design."