AEC definitions
A keynote is a number on a drawing that refers to a legend. The legend states the requirement, often by naming a specification section instead of writing the product on the sheet. The same number means the same thing wherever it appears.
Definition
Keynotes exist so drawings stay graphical and the specification stays in charge of products. A bubble that says 09 21 16 is pointing at gypsum board assemblies, not describing them in full. General notes apply to the whole sheet or the whole set. A keynote applies where it is placed. Local text notes, written out next to one condition, should be reserved for information that is not worth a key. Mixing all three without a rule is how the same wall is specified twice, differently.
In depth
Office standards differ. Some use specification numbers as the key. Some use a short code and a project legend. Either works if every sheet reads the same legend. A detail sheet with a private list of keynotes that reuses numbers from the plan is a trap.
When the spec section changes, the keynote text has to change with it. A key that still says the old section is a conflict, even if the bubble did not move.
If keynote 4 sits on one partition type, only that partition gets that requirement. Do not assume nearby walls are included. If you meant the whole floor, the note belongs in general notes or on a partition-type legend that the plan tags.
Crowded keynotes that land between two details will be read as applying to both. Put the flag on the material it describes.
A keynote that reads 'paint' is incomplete if section 09 91 00 is where sheen, coats, and primer live. The keynote's job is to point. Copying a paragraph of spec onto the drawing creates two documents that will diverge at the first addendum.
Division 01 often says the specifications govern products. A keynote that names a manufacturer the spec does not list is the kind of conflict that clause is about.
General notes are the rules of the sheet: dimensions, references, 'do not scale.' Keynotes identify materials and assemblies at a point. Local notes give a dimension or an instruction that is unique. Reviewers should check that a local note does not contradict a keynote on the same detail.
If everything becomes a keynote, the legend turns into a second specification nobody maintains. If everything is local text, the sheet cannot be updated consistently.
BIM tools can tag elements with keynotes. The issued sheet still needs the legend printed, because the PDF is what many readers have. A tag whose legend was not placed on the sheet is a number with no meaning.
Confirm the tag is visible at the plot scale. A keynote that disappears when the sheet is published was never issued.
Examples
Keynote 09 29 00 on a wall section points to gypsum board, specified in that section. The drawing does not name a brand.
The same keynote number on the floor plan and the detail legend means two different assemblies. The legends are corrected before issue.
A local note says 'sealant by installer' beside a joint that keynote 07 92 00 already identifies. The local note is removed so one instruction remains.
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