Hole Pattern Errors
Hole pattern errors — wrong spacing, wrong edge distance, missing holes, extra holes — are the most common type of shop rework from detailing errors. A member with 4 holes drilled where 5 were required must be re-drilled (if the geometry allows) or scrapped. A member with holes 1/4" off the designed spacing may not bolt up to its connecting member and requires new material. These errors are prevented by the three-way verification (drawing vs. model vs. CNC file) before any file is released.
Cope Dimension Errors
A cope that is 1/4" too shallow blocks the erection of the intersecting member. A cope that is 1/4" too deep may penetrate the fillet and create a stress concentration. Cope dimension errors are detected during erection — when the member is already in the air and the crane is waiting. Field coping is possible but requires ironworker skills and equipment, inspection documentation, and EOR notification. It is always more expensive than getting the cope right in the shop.
Member Length Errors
A member cut 1" short cannot be extended — it must be replaced. A member cut 1" long can sometimes be field-trimmed if the excess is accessible and the trim is approved. Member length errors most commonly result from using a working-point-to-working-point dimension without applying the correct setback for the connection geometry — a common error when connection details are not finalized before cut lists are generated.
Material Grade and Section Size Errors
A shop drawing that specifies W14x132 where the EOR required W14x145 will produce a column that fails the mill certificate check — and may require replacement if the structural analysis cannot justify the lighter section. Material grade errors are equally serious: fabricating a gusset plate from A36 when A572-50 was specified may produce an under-capacity connection that passes visual inspection but fails under the design load combination. These errors stem from incomplete model setup at project start or from manual BOM editing that bypasses the model's grade attributes. The AISC Code of Standard Practice Section 5 places responsibility on the detailer to accurately reflect the grades shown on EOR drawings in every shop drawing callout.
Weld Symbol Errors and Omissions
A missing fillet weld symbol on a shear tab connection means the welder has no instruction for that joint — and different welders will interpret the omission differently. Some will apply a minimum weld; others will leave the joint unwelded. Under AWS D1.1 Table 5.4, minimum weld sizes are prescribed by base metal thickness, but these minimums exist to prevent cracking — they are not connection design specifications. A detailer who omits weld symbols is transferring connection design responsibility to the shop floor, where it does not belong. Every weld on every detail must carry a complete AWS A2.4 symbol with size, length, type, and process specification.
The Cost Differential: Drawing vs. Shop vs. Field
Industry data consistently shows that a detailing error costs approximately 1x to fix on the drawing, 10x to fix after the member is fabricated, and 100x or more to fix after the member is erected. A missing hole callout caught in drawing QA takes 15 minutes to add. The same error caught during assembly requires re-drilling or new material — potentially a full day of shop labor. The same error caught at 50 feet in the air requires an ironworker, a crane hold, an EOR call, and sometimes a replacement member delivered to the site. Investing in front-end drawing verification is the highest-return quality activity in the fabrication workflow.
Preventing Rework Through Systematic QA
The most effective rework prevention protocol combines three independent checks: model-to-drawing comparison by the original detailer, independent drawing check by a second team member not involved in the original work, and CNC file validation before any NC file is released to the shop. Each check catches a different error category — the detailer catches their own oversights during model comparison; the independent checker catches systemic issues the author's familiarity masks; and CNC validation catches the gap between the drawing's intent and the machine's interpretation. At Tectonix, all three checks are documented and logged before any release.
- Model-to-drawing comparison: verify dimensions, hole groups, and connection geometry match the 3D model
- Independent checker review: second reviewer confirms weld symbols, material grades, and cope dimensions
- CNC preview validation: NC file plotted against drawing before release to shop floor
- Edge distance audit: all bolt holes verified against AISC Table J3.4 minimum edge distances
- Revision cloud confirmation: all EOR review comments tracked to specific drawing changes
When Rework Is Unavoidable: Documentation and Recovery
Even with rigorous QA, some errors reach the production floor — driven by late design changes, addendum revisions incorporated under schedule pressure, or the simple reality that complex connections have many variables. When rework is required, the correct response is immediate documentation: photograph the defective condition, record the piece mark and drawing revision, identify the root cause (detailer error vs. design change vs. fabrication execution), and notify the project manager within 24 hours. Detailer errors are corrected at the detailer's cost; design-change-driven rework is a change order. Clear documentation at the moment of discovery prevents cost attribution disputes weeks later when memories are imprecise and the paper trail has thinned.