Second Story Deck Drainage System

floorsforsure

The problem: 25 year old, second story deck over garage, is leaking. The existing deck is slopped to shed water from one end to the next with a box and channel to catch and expell water.the box is bad as is the chanel and the water is soaking through the tile and dry pack before it ever reaches the box. The client wants to keep existing tile. I have found a acrylic waterproofer for the surface but I'm lacking a solution for a drainage system.