Lorcan O'Herlihy, the Irish-born Los Angeles architect who insisted that the most ordinary buildings, including affordable apartments and supportive housing, deserved the full measure of an architect's imagination, died on June 14, 2026. He was 66. His death was confirmed by his firm, Lorcan O'Herlihy Architects, the practice he founded and led for more than three decades.

He was born on September 14, 1959, in Dublin, Ireland, into a family steeped in the arts. His father, the actor Dan O'Herlihy, had trained as an architect before turning to film, and Lorcan spent much of his childhood moving among the great cities of the world as his father worked. That early immersion in urban life left an imprint he would carry into a career devoted to how people live together in dense places, as Architectural Record noted in recalling his life.

He studied architecture at California Polytechnic State University in San Luis Obispo, graduating in 1981, and later pursued graduate study at the Architectural Association in London. His apprenticeship read like a tour through late-century architecture itself. He worked at Kevin Roche John Dinkeloo and Associates, at I. M. Pei and Partners, where he contributed to the team behind the Grand Louvre Pyramid in Paris, and at Steven Holl Architects. In 1994 he set out on his own, founding Lorcan O'Herlihy Architects, known to nearly everyone as LOHA, in Los Angeles.

From that base he built a body of work that quietly reshaped how his adopted city thought about housing. Where many saw density as a compromise, he treated it as an architectural opportunity, designing courtyards, shared balconies, layered facades, and generous thresholds that drew neighbors into contact rather than walling them apart. Projects such as Formosa 1140 in West Hollywood, Mariposa 1038 in Koreatown, the MLK1101 supportive housing, and the modular Isla Intersections in South Los Angeles demonstrated that buildings for people of modest means could be as inventive and humane as any luxury commission. As the Los Angeles Times observed in an appreciation by Sam Lubell, he changed the texture of the city for the better.

His guiding conviction was simple and durable. "We embrace architecture as a social act," he liked to say. "It can enliven a community." He gave that idea book length in Architecture Is a Social Act, published in 2020, and he lived it in practice, pushing his studio toward work he believed carried genuine consequence. Standing in the finished Isla Intersections, he once reflected, "I really like this place. What can I say? I always feel good about being here. I feel this is what I want to do as an architect, yeah?"

The profession returned his commitment with its highest honors. He was elevated to the American Institute of Architects College of Fellows in 2009, having been named an Architectural League of New York Emerging Voice in 2004. In 2021 he received the AIA Los Angeles Gold Medal, the chapter's top award, as recorded by AIA Los Angeles. He later earned the AIA California Maybeck Award and the AIA California Lifetime Achievement Award, among more than 200 honors that LOHA collected over the years. Under his direction the firm completed over 100 projects across three continents, opened a second office in Detroit in 2016, and, in March 2026, transitioned to a collective ownership structure that elevated seven longtime collaborators into leadership.

He was also a generous teacher, holding faculty and visiting appointments at the University of Southern California, SCI-Arc, Columbia University, Carnegie Mellon University, Pratt Institute, the Cranbrook Academy of Art, and the Architectural Association, as detailed by ArchDaily. For the architects who passed through his studio and his classrooms, his example argued that ambition and social purpose were never at odds. The writer Greg Goldin, a longtime collaborator, said the work "gave him the sense that what he was dedicating himself to had meaning in its own right. And that it had a place in Los Angeles."

Lorcan O'Herlihy is survived by his wife, Leila, and their twin sons, Daire and Darcy. His legacy is written across the streets of the city he made his home, in apartment buildings and supportive housing that carry themselves with grace, and in a generation of designers who learned from him that a roof over someone's head can also be an act of optimism. He believed that good design was not a luxury reserved for the few but a civic responsibility owed to everyone, and the neighborhoods he touched are warmer, more welcoming, and more human for the way he answered that call.