I have 10' ceilings and it fits quite nicely, but It would be perfect for a 9' ceiling. However, what you need to be aware about is this needs to mount to a ceiling or door jamb. It is very top heavy. It probably would not fall over from a cat climbing over it, but it might them less willing to have fun on it.  I have mine mounted in this door way and it is really sturdy. My cats run all over this thing and hang all over it as well. Also if you need to move this thing will break down and fit easily into a moving box. I was thinking about making one of these myself. Do yourself a favor and don't bother. I am not sure I could buy the individual pieces (carpet, wood, hardware, etc) and build it cheaper. I did get this on sale for 70% off.