Celadon at 9th and Broadway in San Diego, Calif. Bess Adler / Thornton Tomasetti.

Celadon at 9th and Broadway



Located in San Diego’s downtown district, Celadon at 9th and Broadway is a mixed-use development offering 250 affordable residential units, four stories of retail, amenity and commercial office space, and three levels of subterranean parking. Thornton Tomasetti provided structural engineering for the project, which totals 17 stories and 238,000 square feet.

The housing units are a combination of 300-square-foot flats; 400-square-foot studios; and 600-square-foot, one-bedroom residences. Extensive open spaces along with landscaped plazas at the first, fifth, and 15th floors are designed to encourage interaction among residents and building patrons. Featuring sustainable enhancements such as an eco-roof, photovoltaic solar panels, efficient mechanical systems, and drought-tolerant planting, the project is expected achieve LEED Silver certification.

All floors from the second level, up through the roof level, are composed of post-tensioned slabs. Reinforced concrete with conventional reinforced slabs are present at the ground and basement levels. The seismic system consists of reinforced concrete shear walls at the elevator and stair cores. The main project challenge was minimizing the structural element to make it fit within the small architectural footprint and unit layouts. Thornton Tomasetti reduced the building mass by 10 percent to 15 percent with changes to the existing concept design done by another firm. Thornton Tomasetti achieved the biggest gain by changing the residential floors from conventional 10-inch-thick concrete flat plates to eight-inch post-tensioned flat plates.

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