Florida’s first supertall is climbing a floor every 10 days, and the engineering behind it says more about value engineering than about height. The Waldorf Astoria Hotel & Residences in downtown Miami has passed 870 feet on its way to 1,049, ENR reported Oct. 21, with topping out expected later this year and completion in 2028.
The tower is nine glass-wrapped cubes stacked off-center, each shifted from the one below. Property Markets Group is the developer, Carlos Ott did the design, Sieger Suarez Architects is architect of record and John Moriarty & Associates is general contractor. CHM Structural Engineers designed the frame, Capform holds the concrete package and Supermix supplies the mix.
Supertall structural design: the core, the braces and the damper
Offset blocks look good in renderings and make engineers nervous. Here a 75-foot-by-75-foot concrete core takes the torsion that strong winds put on the shifted massing. Capform CEO Francisco Anderson said it’s larger than any core his firm has built.
Cubes 2 and 9 need more than a core. They use a three-dimensional transfer system with diagonal braces that run over several floors to move gravity loads back to the structure below. Cube 9 cantilevers 25 feet, the project’s biggest offset. “The 25-ft cantilever on Cube 9 has proven to be a challenge,” said Ryan Shear, PMG’s managing partner.
Near the top, a 1,000-ton steel tuned mass damper will counter sway so residents don’t feel it. Miami requires structural peer review on towers like this, so none of these systems went in on one firm’s say-so.
High-strength concrete and a faster forming system
The original design called for 16,000-psi concrete. Value engineering enlarged some columns and added rebar so the job could use 12,000-psi concrete instead. That’s the trade worth noticing. A 16,000-psi mix is harder to source, test and place consistently in South Florida heat, and bigger columns and more steel are a known quantity for a concrete sub. The tower will take about 130,000 cubic yards of concrete and 23,000 tons of rebar.
Capform also redesigned its vertical wall-forming system, which Anderson estimates cut vertical formwork time by about 30%. That estimate is his, not a measured comparison, but it lines up with the 10-day floor cycle Shear described.
An 18-foot mat on a high water table
Before any of that, the site took about a year of ground improvement: deep soil mixing, trench soil mixing walls and more than 300 auger-cast piles, mostly about 160 feet deep. The June 2024 mat pour ran roughly 28 hours and placed 12,400 cubic yards in an 18-foot-thick slab, with 3,900 tons of rebar and more than 1,200 truck deliveries. Capform adapted a local mix with a newer plasticizer and more slag to keep the heat of hydration in check.
Mass concrete thermal control is getting attention on tall work everywhere. Houston Methodist’s new tower hangs on a 27-foot-deep transfer girder poured with 8,000-psi concrete. The Miami job’s lesson is simpler: the most useful structural move on Florida’s tallest building was taking 4,000 psi out of the spec.