CAD layer name decoder

How a layer name is built

A conforming layer name is a sequence of fields separated by hyphens, and the order is fixed. A discipline designator comes first: one required letter, optionally followed by a second that names a sub-discipline. Then a major group of exactly four characters, which is required. Then up to two minor groups, also four characters each, which are optional. Then a single-character status field, also optional.

So A-WALL-FULL-N reads as architectural, walls, full-height, new work. The fields cannot be reordered — that is permitted under ISO 13567 but not under this standard.

Why position decides the meaning

The same four characters can appear as a major group in one name and a minor group in another, meaning different things. STRS is a major group for stairs, and also a minor group under A-FLOR for stair treads shown on a floor plan. GRID is a major group in the structural discipline and a minor group under A-CLNG for a ceiling grid.

A decoder that simply searched both tables for a match would return whichever it found first, and would be wrong a great deal of the time. This one reads strictly by position, which is the only thing that actually disambiguates them.

Most drawings do not conform

Firms extend the standard, shorten it, inherit half of it in a template and invent the rest. That is normal, and it is why this reports a field it does not recognise rather than guessing at one. An unrecognised code usually means a house convention, not a mistake.

Two cases are worth knowing. Every discipline reserves the letters J and K for sub-disciplines a firm defines itself, so AJ- is legitimate and its meaning lives in the drawing set rather than in the standard. And a name built for ISO conceptual conformance fills unused fields with placeholder characters instead of omitting them.

What is here, and what is not

This carries the twenty-one discipline letters, the status codes, and the major and minor groups an architect or interior designer meets most often — a subset in both cases. The sub-discipline tables are not here, and neither is the full list of several hundred groups.

The standard is a paid publication of the National Institute of Building Sciences. This is a reading aid and it is not a substitute for the document, nor an authority on it.