There is a problem with exporting stairs into IFC: the treads are always visible.
In a concrete stair when the treads are turned on, the concrete part of the stair is lower by the amount of the tread 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 treads.
The procedure is to turn off the visibility of the treads in the 3D view and in IFC setting make sure the export uses only the visible elements. The treads show in the IFC export model.
If you turn off the treads (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.
