Joseph Chase, AIA, principal at SOM. “The client wanted dou-ble-pane, high-performing glass as part of an insulated high-per-forming façade.” Designed as a state-of-the-art, innovative office building that inspires and encourages workplace collaboration, One Flagler spans 270,000 ft 2 along the Intracoastal Waterway. Twenty-five stories high, with panoramic water and city views, the LEED gold-certified structure offers not only office space to its tenants but also fine dining, fitness, and conference facilities. Preglazing and Hidden Joints Make for a Seamless Profile The structure of One Flagler is cast-in-place concrete with post-ten-sioning elements. “We actually started the project out from the perspective of doing cast in place with structure and façade as a sin-gle element,” Chase explains. “We ended up with precast concrete for two fundamental reasons: it was far superior for the aesthetic we wanted and, secondly, precast concrete was so much faster.” Preglazed white architectural precast concrete panels with a burnished finish compose the building’s exterior façade. SOM designed the panels to provide integral sunshade elements, with projections of 2 ft 6 in. and preinstalled 8 ft 4 in. × 10 ft 11 in. low-E insulated windows for ultra-clear visibility along with ther-mal performance. “The precast concrete option always assumed the preglazed approach,” says Chase, “because it’s a faster install and [offers] better-quality seals and weatherization. We wanted to limit seal-ant work in the field.” Chase notes that the depth of the window-sills also helped make the building more efficient by limiting glare and providing inherent self-shading. The team started the color sampling process for the architec-tural precast concrete early in the game. “The client really wanted a building that appeared like stone,” Chase says. “GATE Precast came to the table with a crushed limestone and natural sand ag-gregate and worked with a variety of additives to get the right shade of white, followed by a burnishing process after the panels were released from the molds.” Trosset says creating the burnished finish was the most chal-lenging part of manufacturing the panels. “When you pour archi-tectural precast, you sandblast to expose a matrix of materials, but with a burnished finish, you’re just knocking off the cement paste so you don’t have that same surety of consistency,” he explains. “There was a big learning curve there to take such a low-exposure finish and make it consistent for 1000 pieces, but it was a huge success. Those panels not only look like stone but feel like stone.” Precast Concrete Offers Puzzle-Piece Fit GATE Precast, now a part of Wells, worked with SOM in a de-sign-assist capacity to create a modern and clean exterior façade, beginning panel manufacture in October 2022. The team gave ex-tra attention to panel joining, so that panel jambs and sills would tuck behind adjacent panels to conceal joints and create a more seamless appearance. The panels essentially fit together like puzzle pieces, overlap-ping slightly in both directions. This clever design not only hides the joints between panels; it also keeps them watertight. Chase indicates the hidden joints gives the building “a more monolithic, classical look.” The team also developed special corner panels made as one solid piece, so there are no corner joints either, making the corner pieces stronger and more watertight as well. The project included 48 unique panel types. Most of the pan-els were double module units with double sills. Precast concrete installation was occurring simultaneously with concrete podium construction. From level 7 and higher, the panels were fairly typ-ical and repetitive, according to Trosset. “We had some panels, column wraps, and beam wraps around steel, but everything else was mostly donut pieces.” They also used donut panels on the parking structure, but without windows. To shape large, bulky parts of the panels, GATE used lightweight expanded polystyrene foam cut with a computer-controlled ma-chine to form the inside of the panels. This made them much lighter and easier to handle during construction without chang-ing their appearance or load capacity. The largest panel measured 20 ft × 10 ft 9 in. and weighed 28,500 lb. GATE and SOM worked to-gether to optimize panel size to fit on trucks and be easily hoisted up by crane. Because panel installation was occurring simultaneously with construction of the podium, the erection crew worked night shifts with tower cranes to attach the panels. According to Trosset, GATE’s installation team was typically 7 to 10 floors behind the cast-in-place team. Trosset didn’t really see the night work as a challenge: “When you look at the lack of traffic and pedestrians, it offers a different kind of efficiency.” The installation team erected five to six panels per shift. Most of the panels were bolted rather than welded connec-tions due to preglazing. To eliminate the institutional look of joints, GATE Precast, now a part of Wells, reduced the header and vertical sections so that panels on the next floor would swallow the profile below and hide the joint. They used the same process in the jamb for adjacent panels. Thus, all the joints were shifted under the head or on the inside of the vertical jambs. Of course, that created its own challenge, according to Trosset: “Once you set the first panel, you had to work around the building in that flow. So sequencing was critical.” Panel installation took 39 weeks. Completed in 2025 and fully leased, One Flagler reflects what SOM calls “the rich tradition of Florida’s tropical modernism,” presiding like a lighthouse over the entry to West Palm Beach at the Royal Park Bridge. “The building’s sculptural trellis frame, intersecting volumes, and staggered terraces were meticulously engineered to optimize not only aesthetics and tenant experience, but also environmen-tal performance,” says Rathlev. “Its excellent long-term durability allows for more efficient material use and quality control, helping the project align with its LEED gold certification goals, too.” ASCENT, FALL 2025 33
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