The Case for Independent Checking
Research in engineering practice consistently shows that independent review catches errors that self-review misses — not because the original author is careless, but because the brain fills in expected information during self-review. A drafter who drew a cope and then checks the drawing 'sees' the cope dimensions even if they are wrong. An independent checker sees only what is on the drawing and flags anything that is missing or inconsistent.
How Independent Checking Is Organized
On large projects, a dedicated checker reviews all drawings before submittal. On smaller firms, checkers are assigned cross-project — the detailer who draws Project A's columns checks Project B's drawings, and vice versa. The key requirement is that the checker not have been involved in producing the drawing being checked. The check result — approval, revisions required, or questions — is documented before the drawing is released.
When Independent Checking Is Required by the Contract
Some project specifications and owner standards explicitly require independent drawing checking. Government projects, healthcare facilities, and critical infrastructure projects often mandate that shop drawings be checked by a qualified reviewer not involved in their preparation. When this requirement appears in the spec, the detailer must be able to demonstrate that independent checking occurred — which is why a QA/QC log naming the checker is valuable regardless of whether the contract explicitly requires it.
What the Independent Checker Looks For
An independent checker's review differs from the original drafter's QA pass because the checker approaches the drawing cold — without knowledge of the design intent or the connection's design basis. The checker should verify: that every dimension needed for fabrication is shown (no missing dimensions that require shop-floor assumptions); that bolt callouts include grade, diameter, and installation method; that weld symbols are complete per AWS A2.4; that material grades appear on every member and plate; that cope dimensions match what is physically required by the connection geometry; and that the drawing's piece mark and revision letter match the current BOM and revision register. A systematic checklist prevents checkers from focusing only on what they find interesting and skipping items they find tedious.
Model-to-Drawing Comparison as a Checking Tool
The most effective independent checking technique for 3D-extracted drawings is a model-to-drawing comparison: the checker opens both the Tekla model and the drawing, and verifies that the drawing's dimensions match the model geometry for at least 10 key measurements per drawing. This catches the category of error where a model was changed after the drawing was extracted — the drawing still shows the old geometry. Tekla flags drawings that are 'not up to date' relative to the model; the checker should treat any not-up-to-date flag as a mandatory recheck before release. SDS/2 has a similar drawing-update notification system.
Documenting the Check Result
Independent checking should leave a paper trail. The checker documents: the date of the check, their name, the drawing number and revision checked, a pass/fail outcome, and any items requiring correction. This log serves multiple purposes: it demonstrates due diligence to the EOR if a drawing is later questioned; it provides a record of what the checker found for the project PM; and it creates accountability for the checking process itself — checkers who know their work is logged tend to be more thorough. The AISC Quality Certification program (AISC 207) for fabricators references quality documentation requirements that checking logs support.
The ROI of Independent Checking
The cost of independent checking is typically 15 to 25 percent of the original drawing production time per drawing. The cost of a first-cycle 'Revise and Resubmit' from the EOR, including the revision, a new submittal, and the 2 to 4 week delay, is typically 60 to 100 percent of the original drawing production cost, plus the schedule impact. The cost of a fabrication error that survives into the shop and produces rework is several multiples of the drawing cost. Independent checking is the most cost-effective quality investment in the detailing workflow, with a break-even at catching one error per 20 to 30 drawings — a rate any credible checking process exceeds.