What is a drawing legend?
A drawing legend, or key, is the list of symbols, hatch patterns and markers used on a construction drawing, together with what each one means. It usually sits alongside a block of numbered notes that add information the linework cannot show: materials, workmanship, finishes or dimensions to be checked on site. In Dutch practice both parts together are called the renvooi, from the French renvoi, meaning a reference.
Two jobs on one sheet
- The key. It explains hatches (brickwork, concrete, insulation, soil types) and symbols for electrical and mechanical services, levels and similar markers. Without it, a hatch pattern is often ambiguous to anyone outside the office that drew it.
- The notes. Numbered text covering anything that is hard to draw. On some drawings the notes grow long enough to act as a short specification on the sheet itself.
Do not confuse either with the title block, which holds the project name, drawing title, scale, date and revision, even though it often sits right next to the legend.
Application: reading a legend properly
- Read the legend before the drawing. It tells you which conventions the designer used, and those differ between practices.
- Follow the references. A number or letter on the drawing points to a note. If a number has no matching note, raise a query.
- Check the revision. Confirm from the title block that you are working from the current issue; notes are often changed at each revision.
- Resolve conflicts, don’t guess. If a note contradicts the specification or a detail drawing, ask the designer which document takes precedence.
Common mistakes
- Assuming you recognise a hatch without checking the key, when the practice uses its own convention.
- Skipping the notes because the drawing looks self-explanatory. Workmanship requirements are often hidden there.
- Using symbols on your own drawings that are never explained. Every symbol used belongs in the legend.
- Failing to update notes after a revision, so drawing and text contradict each other.
Related terms
- Detail drawing
- Section drawing
- Building specification
- Roof plan
- Architectural rendering
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.