Direct Answer
Price a design revision by identifying the additional material (weight and material cost), the additional labor (hours to cut, weld, drill the change), the rework cost for any already-fabricated material affected, and a burden for project management overhead. Submit the Change Order Proposal with a detailed breakdown, not a lump sum, to support negotiation.
Full Explanation
A revision change order proposal should include: (1) Material cost: additional steel weight × current market price + mill extras. (2) Labor: detailing hours to revise the model and drawings + shop hours to rework or fabricate the revised pieces, priced at your burdened rate. (3) Rework: scrapped material value + disassembly labor. (4) Schedule impact: if the revision affects your critical path, price the delay impact. (5) Overhead and profit markup. Breaking down the cost by line item builds credibility and makes negotiation more efficient.
What This Means for Your Shop
Many fabricators submit lump-sum change proposals that the GC rejects or negotiates aggressively because there is no supporting data. A detailed breakdown shifts the burden to the GC to identify which line items are disputed — a much stronger negotiating position.
Common Mistakes
Underestimating rework hours. Cutting a shear tab off a finished beam, rewelding a new one, repainting, and re-inspecting takes far longer than the original fabrication. Rework is typically 2–3× the original fabrication time.
Recommended Process
Before submitting a COP, walk through the revision with your shop foreman and estimator to capture all labor touchpoints. Use historical rework data from similar revisions to validate your estimate. Submit with supporting backup — a BOM comparison and hour breakdown.