Revision Clouds and Delta Triangles: How to Flag Every MEP Drawing Change So Reviewers Miss Nothing

AutoMEP Team,

An MEP engineer reviewing printed mechanical drawings marked with revision clouds and delta triangles at a desk.

You keep revision clouds and delta triangles trustworthy by clouding every changed area on every affected sheet, matching each cloud to one numbered delta, and checking the clouds against a sheet by sheet list of what actually changed before the set goes out. When that discipline slips, reviewers, estimators, and field teams miss changes that were drawn but never flagged, and they price or build from an older design.

The failure is rarely dramatic. One duct run moves on the third floor plan, the schedule updates, but the sheet gets reissued with no cloud around the reroute and no new delta in the title block. The change is real, it is just invisible to everyone who relies on clouds to find what moved since the last issue.

How do you cloud revisions so nothing gets missed?

Start from a change list, not from memory. Before clouding, write down every edit made since the last issue, sheet by sheet, in plain language: which system moved, which room or grid area it sits in, and which schedules, sections, or details show the same work. A list with 12 entries should produce clouds on every sheet those 12 entries touch, and any sheet that changed without a list entry is a warning sign.

Cloud the full extent of the change, plus enough context to locate it. A cloud that hugs a single fitting tells a reviewer nothing. Cloud the rerouted run from tie point to tie point, cloud the revised schedule row or the full table when many rows changed, and cloud the note or keynote that changed with the geometry. If a change appears on a plan, a section, and a schedule, it needs a cloud in all 3 places, each carrying the same delta number.

What should a delta triangle match across the set?

One delta number means one issue. Every cloud tied to the current revision carries the same delta, and that number appears in the revision table of every sheet it touches, with the same date and the same short description. When a sheet shows delta 4 in its title block but carries a cloud with no triangle, or a triangle whose number never appears in the table, the set is telling 2 different stories.

Check 3 matches before issuing. First, every cloud on a sheet has a delta beside it. Second, every delta in a sheet's revision table has at least 1 cloud on that sheet. Third, the count of revised sheets in the transmittal matches the count of sheets whose revision tables changed. A mismatch in any of the 3 means the clouding pass is not finished, no matter how correct the design work underneath it is.

Why do revision clouds drift out of sync with the drawings?

Because clouding is usually the last task before a deadline, done by whoever made the edits, from memory, under time pressure. Small follow on edits made after the clouding pass rarely get clouded at all. A valve added during a final check, a tag corrected on a plan, a size fixed in a schedule, each one is minor on its own, and together they can leave 5 or 6 unflagged changes scattered across a 40 sheet set.

The fix is sequencing, not effort. Freeze design edits first, then cloud from the change list, then run the 3 match check, and only then plot or publish. Any edit made after the freeze restarts the clouding step for that sheet. Teams that allow edits after clouding without rechecking are choosing to ship clouds they know may be incomplete.

This is structured, repetitive drawing work where AutoMEP fits. It is a web app where MEP engineers and designers upload an AutoCAD DWG or Revit RVT file and describe the edit they want in plain English, and it returns a native DWG or RVT file that opens in AutoCAD or Revit, with no install, no plugins, and no macros. It supports DWG 2007 and later, and Revit 2024, 2026, and 2027, and its edits include duct and piping routing, conduit, equipment blocks, tags with leaders, dimensions, BOM tables, riser diagrams, shop drawings, and title blocks. New geometry goes on AIA or NCS layers automatically, or on an office's own CAD standard layers when a project uses one, and a licensed professional should review the edited drawing before anyone builds from it.

A clouding workflow that holds up at issue time

Firms that treat clouding as a verification step rather than decoration issue sets that reviewers can trust at a glance. The method needs 1 change list, 1 delta per issue, and a freeze that the whole team respects, even when the deadline is tight.

Frequently asked questions

Should you remove old revision clouds when a new revision is issued?

Follow the project standard and keep it consistent. Many firms keep clouds from the most recent issue only and remove earlier clouds, while keeping every delta in the revision table history. What matters is that the current clouds all belong to the current delta, so a reviewer never has to guess which changes are new.

What do you do when a change is too scattered to cloud neatly?

Cloud each affected area separately with the same delta, and add a clear note on the sheet pointing to the change, for example a general note tied to the delta that names the rooms or systems involved. Scattered work, such as a device swap repeated in 20 rooms, is exactly where a note plus repeated clouds prevents missed scope.

How much does AutoMEP cost?

AutoMEP offers a 7-day free trial on all plans, with Starter at $39 per month, Pro at $99 per month with 3 times the limits and job chaining, and Team at $249 per month with 20 times the limits. Extra usage is $2.50 per unit, capped at $25 per month, off by default on paid plans, and failed jobs and no-change jobs are not counted.