Hi,
Revit itself doesn't use layers at all. When exporting to other formats there is a configuration file that determines which objects go to which layers.
When exporting to IFC (from Revit Structure 200) we use the exportlayers-IFC-IAI.txt settings file. The resulting IFC file has the IFC layer property set to S-COLS for columns, S_BEAM for beams etc.
Hope this helps