The Challenge
A 1960s office building converted to residential with eighteen new stories added on top. Three other firms had quoted a full teardown
The developer had a closing date and a building designed for six floors of offices, not a tower's worth of new load. Three firms had quoted a full teardown, and that math killed the deal. The existing structure dated to the 1960s, with foundations that had never been tested beyond their original design loads and a lateral system not conceived with a vertical addition in mind. Before anyone could determine whether the building was worth saving, someone had to actually look at what it could carry.
Our approach
We investigated the foundations first and found real reserve capacity the original drawings never credited. By routing the new loads through the existing core rather than introducing new load paths, we limited strengthening to the areas where the numbers actually demanded it. New columns were positioned to work with the existing grid rather than fight it, keeping the floor plates clean and the construction logic straightforward. We modeled the construction sequence in detail with the contractor so the addition could rise while lower floors were already being fit out, compressing the overall schedule.
The outcome
The building kept its structure, the developer kept their deal, and the project came in on a schedule no teardown could match. The eighteen-story addition went up while the lower floors were being converted below it, cutting overall delivery time significantly. Embodied carbon came in 52% lower than new construction, partly by design and partly because keeping an existing structure is simply less material than replacing it. The project became a case study in what a thorough structural investigation at the front of a deal is actually worth.
+18
Stories added to existing frame
16 mo
Saved vs. teardown + rebuild
52%
Lower embodied carbon
“They were the only firm that actually looked at the building first. Then they made the numbers work.”
Mark Callahan, Managing Director, Eastbridge Capital
