No worries, it is rare if we have a single 'group' for any material. We ussually have a structural and non-structural application of building materials and group these all together in their own categories (concrete, bricks, plywood, gypsum board, etc etc) by ID. And some categories like concrete have even more subdivision to help with correct building material intersections (prefab v.s. on site etc).
Erwin Edel, Project Lead, Leloup Architectenwww.leloup.nl
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