What Clashes Actually Cost When Found in the Field
A beam that clashes with a ductwork main 2" too high requires field modification: the duct is rerouted, or the beam is field-coped and a supplemental angle is welded on. The mechanical sub charges for duct rerouting; the ironworker charges for field modification; the GC charges for coordination; and everyone loses a day of schedule. A beam that clashes with a sprinkler main in the same location requires the same sequence, plus the fire protection engineer must redesign the drop pattern for that zone. Multiply this by 15–20 clashes on a medium-complexity project and the cost is material.
How Steel Is Typically Involved in Clashes
Structural steel appears in clashes in several common patterns:
- Beam top flanges that prevent duct mains from achieving required clearance to finished ceiling
- Steel columns that conflict with planned plumbing chases
- Diagonal bracing members that occupy space needed for mechanical equipment access
- Moment frame continuity plates that block mechanical penetrations through beam webs
- Miscellaneous steel — stairs, mezzanines, platforms — that conflicts with overhead piping
What the Detailer's Model Needs to Enable Clash Detection
For the structural model to function as a coordination tool, it must include all primary members at actual section profiles, connection geometry at LOD 300 minimum (plates, gussets, end conditions), all miscellaneous steel that occupies meaningful volume, and all embeds. Omitting misc steel from the coordination model is the most common reason structural-related clashes are found in the field rather than in the model — misc steel runs directly through the same floor spaces as MEP systems.