There is a problem with exporting stairs into IFC: the threads are always visible.
In a concrete stair when the threads are turned on, the concrete part of the stair is lower by the amount of the thread height. If you need to export the IFC model of only the concrete elements the problem is that there is no way of turning off the threads.
The procedure is to turn off the visibility of the threads in the 3D view and in IFC setting make sure the export uses only the visible elements. The threads show in the IFC export model.
If you turn off the threads (not in the view, but as the element of the stair) then the geometry of the stair is wrong because there is too much concrete in that model.
