Direct Answer
An RFI response sketch (SK drawing) is a freehand or CAD-produced drawing issued by the engineer in response to an RFI — clarifying, modifying, or adding to the design. SK drawings carry the same contractual authority as formal design drawings once issued with the engineer's signature and project reference. They must be incorporated into the detailing model and can trigger change orders if they add scope.
Full Explanation
SK drawing characteristics: (1) Usually numbered sequentially (SK-01, SK-02, etc.) and referenced to the RFI that prompted them. (2) Carry the engineer's seal or signature when they constitute a design change. (3) Supersede conflicting information in the original design drawings for the specific condition they address. (4) Must be incorporated into the detailing model — the detailer revises the model and issues updated piece mark drawings with a revision cloud referencing the SK number. (5) Stored as part of the project record in the CDE.
What This Means for Your Shop
SKs that add material or change connection types are change order triggers — even though they're framed as 'clarifications.' Review every SK against your original contract scope. If the SK changes what you build, notify the GC of the potential cost impact within the timeframe required by your subcontract.
Common Mistakes
Implementing an SK without notifying the GC of a potential cost impact, then trying to recover the cost months later. Contract notice requirements for change order claims are strict — missing the notice deadline can forfeit your right to recover.
Recommended Process
When an SK is received, circulate to the project manager and estimator within 24 hours. The estimator assesses cost impact. If cost-impacting, issue a written notice to the GC within your contract's notice period (typically 10–21 days).