The revision block is the small table, usually just above or beside the title block, that records every change made to a drawing after it was first issued. It is the part of the sheet people read last and should read first: it tells you whether you are holding the current version and what changed since the one you saw. In our studio in Vilnius we treat it as the drawing's history in five columns.
What a revision block contains
| Column | What goes in it |
|---|---|
| Rev | The revision code: a letter, a number, or a status code such as P01 or C02 |
| Date | The issue date of that revision |
| Description | A short, specific note: "Stair 2 widened to 1200 mm", not "general update" |
| By / Chk / App | Initials of who drew, checked and approved the change |
| Status (optional) | For information, for tender, for construction |
An example
| Rev | Date | Description | By | Chk |
|---|---|---|---|---|
| C | 2026-10-12 | Door D-04 swing changed; corridor width noted | AB | CD |
| B | 2026-09-28 | Structural grid updated to engineer's Rev 2 | AB | CD |
| A | 2026-09-10 | First issue for coordination | AB | CD |
Whether the newest row sits at the top or the bottom is an office convention; what matters is that everyone on the project reads it the same way.
Revision codes: letters, numbers and status codes
- Letters then numbers: a common pattern is letters (A, B, C) for issues before construction and numbers (0, 1, 2) once a drawing is issued for construction.
- Status codes: projects run under ISO 19650 often use a status letter plus a number, for example P01, P02 for preliminary issues and C01, C02 for contractual ones.
- Whatever the system, the code in the revision block must match the tag next to the revision cloud on the sheet and the code in the file name.
How the revision block works with clouds
The revision block says what changed; the revision cloud and its delta tag show where. Each cloud on the sheet carries a tag with the revision code, and that code points to a row in the revision block. See revision clouds on drawings for the conventions.
Mistakes that cause real problems
- A vague description. "Updated" forces everyone to compare the whole sheet.
- A drawing that changed without a new row. The most dangerous one: two different sheets carry the same revision code.
- A file name that does not match the block. "A-101_RevB.pdf" with Rev C in the table means someone will build from the wrong one.
- Revision rows that do not match the clouds. A tag on the sheet with no row in the block, or the other way round.
Checking a revision in practice
When a new revision arrives, read the block first, then confirm the change on the sheet. Clouds show where the author says something changed; comparing the new PDF with the previous one shows everything that changed, including what nobody clouded. In Ncored, the PDF editor we built in our architecture studio, you open the new revision and drop the previous one onto it: added items turn blue, removed items red, the rest grey. It works on Windows and Mac. More in how to compare two PDF files.
Frequently asked questions
Where is the revision block on a drawing?
Usually directly above or beside the title block, often in the bottom right corner of the sheet.
What is the difference between a title block and a revision block?
The title block identifies the drawing: project, sheet, scale, author. The revision block records its history: each revision's code, date and description.
Should the newest revision be at the top or the bottom?
Either, by office or project standard. Keep it consistent across the whole set.
What does Rev 0 mean on a drawing?
In many offices it marks the first issue for construction, following lettered revisions used during design.
Related: architectural title block guide, what is a title block, what is a drawing revision.
Further reading: what is a transmittal, IFC drawings.