Commercial and mixed-use

The steel on a commercial frame is rarely the hard part on its own. Composite floors, braced or moment-frame stability and a transfer structure where a residential grid lands on a retail one are all well-trodden. What makes these jobs difficult is everything the steel has to agree with: a concrete core poured on its own programme, a facade with its own tolerance, services running through beams that were sized before the services existed, and a site where the crane has one position.

Where the cost actually moves

Late change is normal on these frames and is not, by itself, the problem. The problem is late change discovered after material is cut. That is why coordination and detailing are the stages that decide the budget here: a clash-reviewed model and an early advance bill of material are worth more than any efficiency in the frame itself.

Fire protection changes the detail

Intumescent or board protection is applied to a fabricated member, so it belongs in the detailing conversation rather than after it — access for application, what happens at a bolted connection, and which faces are reachable once the member is in place. Where the protection specification is not yet fixed, the detailing assumptions made in its absence are stated on the drawings rather than left implicit.