At 250 feet long and 60 feet tall, the Botanical Building in San Diego is one of the largest lath structures in the world. Since its construction for the 1915 Panama-California Exposition, it has served as a plant-filled fixture of Balboa Park. But after decades of weather exposure, the building’s hundreds of redwood lath strips and original steel frame were deteriorating. Advocacy by nonprofit Forever Balboa Park led to an infusion of state funding for its restoration in 2019, and the 15,000-square-foot structure reopened to the public in December 2024.

Before construction began, the project team removed hundreds of plants and stored those that could be saved at a city nursery. “I think because the building was full of plants, people didn’t notice a lot of the steel deterioration,” says Sandra Gramley, principal at Platt/Whitelaw Architects and the project’s architect of record. The original steel frame required nearly 1,300 individual repairs before it was treated with a protective paint.

“The city was hoping originally that they could salvage some of the wood,” says Jim Summers of EC Constructors, the general contractor, but structural assessments determined that much of it was beyond repair, and other pieces had to be removed to gain access to the steel. The team sourced new, sustainably harvested redwood and reconstructed the building’s open-air shell, lath by lath. Crews also re-created the original windows and arched plaster facades, which had been removed during a 1950s renovation. The restoration, a collaborative effort between the city and Forever Balboa Park, cost about $26 million in state and city funding.