When a shop drawing package comes back for a second review, the reviewer usually checks that the earlier comments were addressed and stamps it. The risk is everything else: a member size, an anchor spacing or a dimension that changed between submissions without a cloud. The reliable way to catch it is to compare every sheet of the resubmittal against the sheets you reviewed last time. Drawing Revision Delta, a Windows app from Automata Labs, matches the two sets by sheet number, shows which sheets changed and where, and lists changed words such as 2x6 to 2x8, all on your own PC.
This guide covers why unflagged changes happen, what one widely used federal specification says about them, and a review routine that does not depend on the submitter’s clouds.
Compare a resubmittal against the sheets you already reviewed, sheet by sheet.
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Why do resubmittals contain changes nobody flagged?
Nobody has to be acting in bad faith. A detailer fixes the items in the review comments, then the fabricator’s engineer updates a connection, someone corrects a typo in a schedule, and the drawing is re-plotted from a model that kept moving in the meantime. Revision clouds are drawn by hand, after the fact, by whoever remembers what changed. Our explainer on revision clouds and delta tags covers how those marks are meant to work.
The result is a package where the clouded items are the ones the reviewer asked for, and the uncomfortable ones are elsewhere.
What does UFGS 01 33 00 say about variations in submittals?
Contracts handle this in their general conditions and submittal sections, so read yours. As one public example, the US Unified Facilities Guide Specification section UFGS 01 33 00 Submittal Procedures (August 2026 edition, read today on the WBDG site) says:
- Contractors must “specifically point out variations from contract requirements” in a transmittal letter or variation submittal, and “failure to point out variations may cause the Government to require rejection and removal of such work at no additional cost to the Government.”
- For Army projects: “Set forth in writing the reason for any variations and note such variations on the submittal. The Government reserves the right to rescind inadvertent approval of submittals containing unnoted variations.”
- Resubmissions are tracked by a numeric suffix: “submittal 18 would become 18.1, to indicate resubmission.”
The responsibility to point out changes sits with the submitter. That protects the reviewer contractually, but it does not stop an unnoticed change from being fabricated. A comparison catches it before the steel is cut.
What should a resubmittal review actually check?
| Check | Question to answer | Where the answer comes from |
|---|---|---|
| Comments addressed | Was each earlier comment resolved as asked? | Your previous review markups |
| Clouded changes | Are the clouded items acceptable? | The resubmittal’s clouds and narrative |
| Unclouded changes | Did anything else change? | A sheet-by-sheet comparison against the last reviewed set |
| New or missing sheets | Were sheets added or dropped? | Sheet list comparison |
| Title block | Revision letter and date updated? | Title block, ignoring it in the comparison |
The third row is the one most reviews skip, because doing it by eye across 40 sheets takes longer than the rest of the review combined. Our general guide on how to compare two drawing revisions covers the manual methods.
How do you compare a resubmittal against the previous set?
- Keep the set you reviewed. Save the exact PDF you stamped, not a later copy. Your submittal log should point to it.
- Put each set in its own folder. One folder for the reviewed submission, one for the resubmission.
- Run the comparison. In Drawing Revision Delta, pick the earlier folder and the later folder. Sheets are matched by the sheet number in the title block. Scanned sheets without a text layer are read with the text recognition built into Windows.
- Mask the title block. A mask over the title block ignores date and revision-letter edits, so they do not flood the results.
- Start with the most changed sheets. The Pairs table shows how much of each sheet changed and sorts the most changed first, and lists sheets that are new or missing.
- Step through each change. Use Overlay (red only in the earlier revision, blue only in the later one), Blink or Side by side. Where both PDFs have text, changed words are listed in plain terms, for example 2x6 to 2x8.
- Compare the result with the clouds. Every change should be either a response to your comments or clouded and described. Anything else goes back as a question.
See every change between two submissions, including the ones without clouds.
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What do you send back when you find an unflagged change?
Specific evidence beats a general complaint. Drawing Revision Delta exports:
- The later revision’s sheets, unchanged, with a revision cloud around every change, saved as one PDF. The clouds are PDF markups, not drawn into the sheets.
- A PDF change report that opens with the changed-sheet list, then one section per sheet, with a SHA-256 hash of every input file, so anyone can confirm which files were compared.
- A sheet summary and a list of every change as CSV files, and PNG snapshots.
A short note works well: “Sheet S-3 shows a change at grid C/4 that is not clouded or described in the transmittal. Please confirm whether this is intended and resubmit with the variation identified.” Attach the clouded PDF.
Is a manual overlay good enough?
For one or two sheets, yes. Many PDF viewers can overlay two pages. The limits show up with a full package:
| Manual overlay in a PDF viewer | Drawing Revision Delta | |
|---|---|---|
| Sheet matching | You pair pages by hand | Matched by sheet number from the title block |
| Plotter or scanner stretch | Misalignment shows as noise | Aligned for shift, rotation and scale, then corrected locally |
| Which sheets changed | Open each one | Pairs table sorted by amount of change |
| Text edits | Visual only | Changed words listed where both PDFs have text |
| Output | Your own markups | Clouded PDF, change report with hashes, CSV |
| Files leave the PC | Depends on the tool | No; nothing is uploaded |
If you already use a desktop PDF suite, our comparisons with Bluebeam Revu and Acrobat Compare Files show where each fits.
Frequently asked questions
Who is responsible for flagging changes in a resubmittal?
Under specifications like UFGS 01 33 00, the submitter must point out variations, and unnoted variations can lead to rejection or rescinded approval. Your contract governs, so check its general conditions and Division 01 submittal section.
Does Drawing Revision Delta work on shop drawings, or only architectural sets?
It compares any two revisions of a drawing set: PDFs, scanned TIFFs and other images, matched by sheet number. Shop drawings from fabricators work the same way as design drawings.
What if the fabricator renumbered the sheets?
You can correct any pair by hand, and sheets that are new or missing are listed so renumbering is visible.
Will it change my files?
No. It reads only the files and folders you pick, and exports are new files.
Try Drawing Revision Delta
Drawing Revision Delta is a one-time purchase in the Microsoft Store with a free trial. There is no account, no sign-in and no telemetry, and drawings stay on your PC. See the Drawing Revision Delta product page for more, and our guide to submittal types for where shop drawings fit in the submittal process.
Review the whole resubmittal, not just the clouds.
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Last updated 22 October 2026. Published by Automata Labs, a software company in Canada.