Thoughts on office-to-residential conversions vs starting from scratch?

I worked on a similar gut rehab in the Flatiron District last year where the original prints didn't match the reality behind the plaster. We found out halfway through that a 1940s renovation had notched several load-bearing members to run plumbing, and the steel was already stressed before we even brought in the new floor slabs. When you start stripping out the partition walls, you lose a lot of that secondary stiffness that’s been helping keep things stable for eighty years.

In my experience, the problem isn't the old steel itself—it’s the lack of real-time monitoring during the demo phase. We’ve started using wireless tiltmeters and strain gauges on the primary columns as soon as the interior demo starts. It adds to the upfront budget, but it's cheaper than having the city shut down the site because a column is bowing three inches out of plumb. If you aren't doing a full 3D scan and structural audit before the first sledgehammer swings, you're basically flying blind. The environmental savings are real, but you have to respect the existing structure's history.

I disagree that the unpredictability is an inherent flaw of the building itself. Most of the time, these "close calls" come down to firms cutting corners on the pre-con structural audit. We just wrapped up a conversion on a 1920s warehouse in Queens, and we spent three weeks just doing 3D laser scans with a Leica RTC360 before a single jackhammer touched the floor. If you're relying on paper prints from the FDR era, you're asking for trouble. The environmental arguement isn't just a "benefit"—it's the only way we meet the new carbon benchmarks. A new build creates a massive footprint before the first tenant even moves in. We used Simpson Strong-Tie FRCM for column wrapping on our last project to boost load capacity without adding the bulk of traditional concrete jacketing. It’s about using modern materials to retro-fit the old skeleton, not just hoping the old steel holds up. If the engineering team is acutally on-site monitoring the shoring loads daily with digital strain gauges, these buckling issues shouldn't happen. It's a failure of process, not a failure of the concept.

It's acutally the introduction of eccentric loading that often catches people off guard, especially when firms start bolting those massive cantilevered balconies onto a riveted frame originally designed for uniform office live loads, essentially forcing a significant bending moment onto the columns that the original engineers never accounted for in thier Euler buckling calculations. If the onsite crew is stripping out the Thermasheath and leaving that decades-old steel exposed to the ambient Manhattan humidity without immediate surface remediation, you're also risking localized corrosion at the gusset plates which subtly compromises the cross-sectional area and the overall radius of gyration.

Seen it a hundred times. These modern crews strip the terracotta or concrete fireproofing off the steel and think they’re just cleaning it up. They don't realize that heavy encasement acted like a corset keeping those old columns straight for a century. You take that off and you're left with a slender member that wasn't meant to stand naked under load. Back in the 80s, we’d have 12x12 oak timbers shoring up every bay before we even touched the cladding. Nowadays, everyone trusts a digital sensor more than a plumb bob. If the building starts groaning, you don't wait for a notification on your phone—you get out.

Quick update — we finally got the situation stabilized. That point about the fireproofing acting like a "corset" was spot on. The crew had stripped the encasement too fast, and the columns couldn't handle the slenderness without that extra support. We've reinforced the steel and improved the shoring. It’s a relief to have the math finally lining up with what’s actually happening.