Architectural drawing symbols are the shorthand that links the sheets of a drawing set together. The most important ones are the north arrow (orientation), section and elevation markers (where a cut or view is taken and which sheet shows it), detail callouts (which enlarged detail covers an area), grid bubbles (the structural grid), level markers (heights), and tags for doors, windows and walls. Most reference symbols carry two numbers: the view number on top and the sheet number below, so 3 over A-301 means "view 3 on sheet A-301".
The symbols you will see on almost every set
| Symbol | What it looks like | What it tells you |
|---|---|---|
| North arrow | An arrow or compass rose marked N | Orientation of the plan; may show both project north and true north |
| Section marker | A cut line through the plan with a circle at each end, split in two, with an arrow showing the viewing direction | Where the section is cut, which way you look, and which sheet shows it |
| Elevation marker | A circle or square with one to four arrows pointing at walls | Which interior or exterior elevation shows that wall, and on which sheet |
| Detail callout | A circle or cloud around an area, with a leader to a split circle | Which enlarged detail covers that area, and on which sheet |
| Grid bubble | A circle at the end of a dash-dot line, with a letter or number | The structural grid line used for setting out and referencing |
| Level / datum marker | A triangle or circle-quadrant with a height value | Finished floor or other levels, such as +3.150 or FFL 100.00 |
| Door and window tags | A small circle, hexagon or rectangle with a number | The row in the door or window schedule for that opening |
| Wall type tag | A small symbol with a code such as W3 | The wall build-up defined in the wall type legend |
| Revision cloud and delta | A wavy outline with a triangle containing a revision code | Something changed in that revision; see the revision block |
| Match line | A heavy line labelled "match line" with a sheet reference | A plan continues on another sheet from that line |
| Break line | A line with a zigzag | The element continues but is not drawn in full |
| Spot elevation | A cross or dot with a height value | The height of the ground or a surface at that point |
How to read a reference bubble
Section markers, elevation markers and detail callouts all use the same split circle. The upper half holds the view number on the target sheet; the lower half holds that sheet's number. A section marker reading 2 over A-301 means: go to sheet A-301 and find view 2. On the target sheet, the view title repeats the same pair, often with the scale, so you can always trace a view back to where it was cut.
North arrow: project north vs true north
True north is geographic north. Project north (or plan north) is a direction chosen so the building sits square on the sheet. When the two differ, many sets show both arrows on the site plan and only project north on the floor plans. Always check which one a sun study, a compass-based description or a site boundary refers to.
Where symbols are defined
Every set should have a legend, usually on a general sheet such as A-001 or G-002, listing the symbols, line types, hatches and abbreviations the office uses. Symbols vary between offices and countries, so read the legend before relying on memory. See architectural sheet numbering for where that sheet sits in the set.
Following references in a PDF set
On paper you flip to the sheet in the bubble. In a PDF set you search for the sheet number or use the thumbnails. In Ncored, the PDF editor we built in our architecture studio, large drawing sets stay smooth to zoom into the small text of a bubble and to move between sheets, on Windows and Mac, and you can cloud or comment any symbol that does not match its target. See how to read construction drawings.
Frequently asked questions
What does a north arrow show on a drawing?
The orientation of the plan. Some drawings show both true north and a rotated project north used to keep the building square on the sheet.
What do the numbers in a section symbol mean?
The top number is the view number and the bottom is the sheet where that section is drawn.
What is the difference between a section marker and an elevation marker?
A section marker shows a cut through the building and the direction of view. An elevation marker shows a view of a wall face without cutting through it.
Are architectural symbols standardised?
Partly. The US National CAD Standard and ISO drawing standards define common symbols, but offices adapt them, so always check the legend on the set.
Related: plan, section and elevation, revision clouds, what is a blueprint.