Drawing revision control: recount quantities when revised drawings arrive

Choose one authoritative drawing version

Record the file and revision used for the count. Include the filename, title-block revision number and date, delivery channel (email or shared folder), and date received so the drawing basis remains traceable.

• Include the revision number and date in the filename. Example: Building101_PowerPlan_R2_20261026.dwg
• Keep previous revisions in an ‘Old versions’ folder rather than deleting them.
• Give the quantity schedule the same revision label as its drawing so they stay paired.

Three ways to identify changes

1. Check revision marks: Start with the title-block revision history, revision clouds and triangle markers. These are the quickest way to identify changes when the designer has marked them.
2. Drawing comparison: Use CAD drawing comparison, or overlay the two revisions in different colors, to identify added, deleted and moved elements. This also helps catch changes without revision marks.
3. Compare by identifier: If the existing schedule records identifiers and coordinates, check each location against the revised drawing for the same symbol. Voltix’s Evidence sheet supports this comparison.

Use the methods together: start with the broad area identified by revision marks, then compare the drawings to catch unmarked changes. Combining methods reduces omissions.

Recount changed areas and update the schedule

Recount only devices within the changed area. Use new identifiers instead of reusing old ones. Retain deleted-device rows with a status such as ‘Deleted (R2)’ so the quantity change between revisions remains traceable.

After updating, recalculate each item total. The difference from the previous revision should equal additions minus deletions. A mismatch can indicate a missed change or a duplicate identifier.

Common revision-control mistakes

• Only some sheets are revised: For example, the power plan may be R2 while the lighting plan remains R1. Record revision numbers separately for each sheet.
• Relying only on revision clouds: Revision marks may omit changes. Use drawing comparison to check beyond them.
• One unit-type revision can affect several buildings: A change to one type plan affects every dwelling that uses it. Calculate building totals from dwelling-unit takeoffsPlease refer to .
• The emailed ‘latest version’: An emailed file may differ from the shared-folder copy. Ask the sender which one is authoritative.