Migrate from ARCHICAD 16 and earlier.
An option allows you to define a Slab core (top or bottom) as its reference plane, or the Slab top or bottom.
Reference planes of Slabs migrated to ARCHICAD 24 from earlier-version projects will all have a Reference plane at the top of the Slab by default.
Relevant topics
Slab Reference Plane
Each Slab has a reference plane which plays a role in intersections with other elements. The ability to flexibly assign a Slab reference plane ...
Switch Reference with Active: Access Elements within the Reference for Editing or Copying
Elements on the Reference cannot be selected or edited.
However, by switching the Reference and Active views temporarily, you can select and ...
Set Custom Slab Edge Angle and Edge Surface
To customize a slab edge angle, and to apply a custom surface to the edge(s) of a slab and/or its holes, select the slab (or just its hole) and ...