jeremy, first thank you for your hint pertaining the inefficiency in my collector.
secondly you are right, the problem is caused by the overloaded version.
i just added the phase and retrieve the rooms as expected.
tx peter
here the code:
fc = FilteredElementCollector(doc) doors = fc.OfCategory( BuiltInCategory.OST_Doors ).WhereElementIsNotElementType() phases = doc.Phases phase = phases[phases.Size - 1] for door in doors: try: froom = door.FromRoom[phase].Id except: froom = -1 try: troom = door.ToRoom[phase].Id except: troom = -1 TaskDialog.Show("Revit","From Room: %s, To Room: %s" %(froom, troom))