The American Institute of Architects provides over 300 label names for the sections, details, legends and text and other layers found in CAD drawings. Label names are made up of an initial and an abbreviation of the layers function or content.
Architectural drawings begin with the initial A, civil drawings with a C, electrical with an E, and so on. Abbreviations are usually self-explanatory. For instance, the layer of a CAD document that contains the doors is listed as A-DOOR Doors. Further, it would be on the 2-yellow layer with the continuous line weight of a number 7 pen.
Each layer in a CAD document must be colored according to the AIA’s standards. For instance, all layers of architectural annotations and dimensions are cyan, while layers referring to electrical safety are red. The example above for doors is on the yellow layer.
The line weight of a layer is also set by AIA standards. For example, as a general rule boundary lines, legends, dimensions, and notations use a number 4 pen, while construction lines, walls, and border and title block use a number 7 pen. Layers dealing with sewers and drainage pipework and manholes, on the other hand, use a number 11 pen line weight.
The AIA CAD Layer Guidelines have been incorporated as part of the National CAD Standard. The diagram below shows AIA standards for layer colors and pen weights.
For the official US National Layering CAD standards: https://www.nationalcadstandard.org/ncs6/pdfs/ncs6_clg_lnf.pdf
To purchase this US National CAD standards document: https://www.nationalcadstandard.org/ncs6/ordering.php