To save a major operation and damaging the wall acertain where the leak is but lifting the floor.
Look at the feed to the shower and see if where the pipe goes up the wall, if water is dripping.
Follow this pipe back towards its source or T off point see if there are leaks there. All dry? then turn off the water to the shower rather than all water even if this entails putting in a stopvalve on the shower pipe/s. Turn the water back on when you'v isolated the shower and get a broom handle and place one end on the pipe and your ear on the other end or side listen move along the pipe the closer to the leak the louder it will sound. And no I'm not joking used that method for finding knocks in car engines it was great for finding a rattleing tappet on the older engines.
If no leaks below the floor then cap the shower feed/s and turn water back on and check again if you can hear the shower pipe in the wall leaking. if not it coulb be the shower to pipe fitting was leaking remake the joint replace the shower.
It's a pain in the arse but better than cutting out the tiles to find the pipe in the wall is not leaking.
bob, October 2012
