Hi Jon
This is what I was told, bearing in mind my ceilings are lath and plaster and a bit bulgy in places:
Fix a piece of wood between the two joists where the rose will sit. (You will have to lift the upstairs floor). Carefully drill four holes in the rose and countersink them - make these with a wood drill bit slightly smaller than the screw so the screws will bite into the rose. Two at opposite edges to line up with the centres of each joist, Mine were about 1inch in from either side of the rose) and two nearer the centre. These will fix into the wooden block. (They end up all in a straight line)
You also need to drill a large enough hole in the centre of the rose to feed the wires through. (Though not too large as you need to screw the light fitting into the rose)
You need quite long screws, if you imagine they have to go through the thickness of the rose, through the ceiling and into your block or joist - I think mine were 4 inches or so).
I also used some no more nails type stuff before offering it upto the ceiling and filled any gaps around the rose and the ceiling.
You then connect up the fitting and screw through the top of the light fitting into the ceiling rose. Use very small pilot holes for these. If the light fitting is heavy you may consider using long screws again so you can screw up into the wooden block.
You do need to have help, one to hold the rose and one to screw.
I found it difficult to locate the rose in the appropriate position so the holes would line up with the joists. In the end I drilled a hole through the ceiling from upstairs either side of the joist just beyond the perimeter of the rose, and used these to guide me.
Others may have a different opinion, and it may be worth mentioning the type of ceiling you've got as the fixing may vary. Perhaps the way I was told is unnecessarily strong, but they are still up!
Hope this helps. I did draw a diagram but I can't work out to paste a picture, it won't seem to let me.
Hope this helps
Amanda
