Reference Guide

Revision Cloud Guide

What revision clouds are, how to read them, revision triangles, revision history blocks, and how to use revision clouds to understand what changed between drawing sets.

Last updated: March 2026•Based on AIA Standards
Why This Matters

Revision clouds highlight what changed between drawing versions. If you miss a revision, you may build to an outdated detail or miss a critical design change. Tracking revisions is also essential for understanding change orders—a change marked with a revision cloud proves when it occurred and impacts schedule/cost.

What Is a Revision Cloud?

A revision cloud is a bubble-shaped outline drawn around an area of a drawing that has been changed. It highlights the specific location of a modification, making it easy to spot what's new or updated without reading the entire drawing.

Visual Appearance
• Wavy/arc outline (bubble cloud shape)
• Drawn around the modified area
• Usually in red or a contrasting color
• Labeled with revision number/letter (1, 2, A, B, etc.)
What They Mark
• New dimensions or text
• Moved or deleted elements
• Changed detail references
• Corrected errors from prior version
• Changes in response to RFIs or code comments
Key Concept: Revision clouds are NOT required—some drawing sets don't use them. But when they're present, they're your roadmap to understanding what changed. Always check for them before starting work on an updated drawing set.

Revision History Block (Title Block)

The revision history block (usually located in the title block or adjacent to it) documents all changes made to a drawing. It's your reference for understanding when and why changes occurred.

Typical Revision Block Contents:
Rev #
Date
Description
1
2/15/2026
Added window detail per RFI #12
2
2/22/2026
Moved electrical outlet per code comment
3
3/1/2026
Increased roof slope for drainage
Revision Letter/Number
Sequential: 1, 2, 3... or A, B, C...
Date Issued
When revision was released
Description
Why the change was made

Revision Triangles (Delta Symbols)

Some drawings use small triangles (delta symbols, Δ) with a revision number inside them, placed next to changed dimensions or text. This is an alternative to (or supplement to) revision clouds.

Where You'll See Them
Next to a dimension that changed (e.g., "24"" with a small triangle marked "2" indicating revision #2). Next to text or notes that were added/modified.
Advantage
Pinpoints the exact changed value. Clouds show a general area; triangles mark the precise modification. Both can be used together.

How to Read & Track Revisions

Step 1:
Check the revision history block. Identify the current drawing revision number/date. Are you working with the latest version?
Step 2:
Scan the drawing for revision clouds. They will stand out visually (usually in red). Note the revision numbers within each cloud.
Step 3:
For each revision number, cross-reference the revision history to understand what changed and why (RFI, code correction, design change, etc.).
Step 4:
If you're comparing an old set to a new set, mark areas you're uncertain about. Request clarification via RFI if the change is ambiguous.
Step 5:
Document in your daily logs or submittals that you've reviewed revisions and are building per the latest version.

Comparing Drawing Revisions

When you receive an updated set, compare it to the previous version to understand all changes. Revision clouds help, but a systematic comparison is best:

Manual Comparison
  • • Overlay new sheet on old sheet (physical or digital)
  • • Look for gaps, shifts, or different callouts
  • • Note all changes in a comparison log
  • • Cross-reference with revision history
  • • Time-consuming but thorough
Using Revision Clouds
  • • Scan clouds marked with new revision numbers
  • • Don't assume unmarked areas are unchanged
  • • Some revisions are subtle (dimension tweaks)
  • • Always verify what changed within each cloud
  • • Fast but only as good as the clouds drawn
Pro Tip: Print both old and new drawings side-by-side. Mark up the new set with a highlighter, circling areas that differ from the previous version. This creates a visual audit trail of all changes.

Common Issues with Revisions

✗
Missing revision clouds: Drawing was changed but clouds weren't added. You may miss critical updates. Always compare old to new carefully.
✗
Vague revision descriptions: Revision history says "minor changes" but actual changes are major. Read the drawing itself, don't rely solely on description.
✗
Subtly different dimensions: A dimension changed from 24" to 24.5"—easy to miss. Revision triangles help; clouds might not capture small text changes.
✗
Conflicting revisions across trades: Structural revised one detail; MEP didn't get the memo. Revision clouds are trade-specific; ask all consultants for their latest marked-up sets.
✗
Building to an old set: Work started on outdated drawings. Revisions issued but field crew didn't get notification. Always verify you have the latest issued set before work begins.

Managing Revisions on Your Project

Create a Revision Log
Track all drawing revisions received: sheet number, revision date/number, key changes, and date implemented on site. This creates a record of when changes were made and what they were.
Distribute Marked-Up Sets
When revisions are issued, print and distribute marked-up copies to all field crews highlighting the changes. Don't expect them to notice revision clouds on their own.
Document Changes for Change Orders
If a revision requires rework or adds scope, attach the marked-up drawings to your change order request as evidence. The revision history documents when/why the change was made.
Clarify Ambiguous Revisions
If a revision cloud marks an area but you're unsure what changed, submit an RFI asking for clarification. Don't guess and build based on assumption.

Related Resources

How to Compare Drawing Revisions
Systematic approach to finding differences between drawing sets.
How to Write an RFI
Asking for clarification on ambiguous revisions.
Construction Daily Log Guide
Documenting when revisions were implemented.
Change Order Guide
Using revisions to support change order requests.

Revisions communicate design changes. Always review the revision history block and carefully examine revision clouds before starting work. When in doubt, ask for clarification. Missing a revision can trigger rework and delays.