(Migrate from ARCHICAD 18 or later)
The default ARCHICAD Library includes a Surface Catalog, containing Surface attributes. Always use the Surface Catalog 21 with ARCHICAD 21, even if you open an older-version project.
The Standard and Additional Surface Catalogs for ARCHICAD 21 together contain the entire contents of the corresponding catalogs for ARCHICAD 18 and later. Adding the older catalogs to your project is therefore superfluous and will result in duplicates.