(Migrate from ARCHICAD 17 or earlier)
The Building Materials dialog box has a “Participates in Collision Detection” checkbox in the Properties panel. This is useful for defining whether particular building components – parts of composite or complex elements – should be exported in IFC, and/or whether they should participate in collision detection.
See Collision Detection.
All Building Materials are migrated with the checkbox ON. (In other words, all migrated Building Materials are set to participate in Collision Detection by default.) To exempt any Building Material, uncheck its box in the Building Materials dialog box.