Direct Answer
Ironworkers are the skilled tradespeople who erect structural steel — setting columns, connecting beams, bolting connections, and field-welding. They work under ironworker union agreements (IABSORIW) on union projects and are trained in rigging, working at heights, bolting, and connection-making. They are distinct from steel fabricators (who work in the shop) and from structural welders (who may be a separate specialty trade).
Full Explanation
Ironworker specialties: (1) Structural — erect structural frames, set columns and beams, make up bolted connections. (2) Reinforcing — place and tie rebar. (3) Ornamental — install architectural metal (curtain wall, stairs, handrail). (4) Riggers — specialized in crane rigging and heavy lift. Structural ironworkers must be competent in: reading erection drawings, rigging and signaling, working at heights with fall protection, operating bolting tools (impact wrenches, TC wrenches), and basic field welding (tack welding for temporary bracing). For union projects, ironworker wages, jurisdiction, and work rules are defined in the labor agreement.
What This Means for Your Shop
Understanding ironworker jurisdiction helps you avoid scope disputes. On union projects, ironworkers may claim jurisdiction over any field handling or modification of structural steel — including field welding and field drilling that you might have assumed was in your scope. Clarify jurisdiction before signing the erection subcontract.
Common Mistakes
Assuming that because the fabricator is doing the erection (self-performing), there's no jurisdiction issue. Union projects have jurisdiction rules regardless of who the employer is.
Recommended Process
On any union project, review the applicable ironworker labor agreement for scope and jurisdiction before signing the subcontract. Identify any scope items that might create jurisdiction disputes and raise them with the GC before work begins.