I'm working on wiring my house and I've run into a problem when cabling down the inside of my exterior facing wall in the kitchen (it's the wall that faces the garden). I'm trying to run a cable from the ground floor to the 1st floor. Basically there is a steel channel at the ceiling of the ground floor behind the plasterboard/drywall that is stopping me fishing a cable rod up through the ceiling. Has anyone run into this problem? How do you get around it?