It is just a projection of the slab, so if you can see the slab layer, you will see the projection.
Sadly slabs don't follow the projection range of story settings.
You could make it with a 0° roof, but then you don't have automatic connection with walls and automatic solving of finish layers through door openings and such.
We treat these dashed lines as 2D annotation, either with objects that have smart story sensitive settings (closed line on one story, dashed on other) or just plain old polylines.
Erwin Edel, Project Lead, Leloup Architecten
www.leloup.nlArchiCAD 9-26NED FULL
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