I have a leaking patio door - so what else in new. However, I haven't seen any posts that describe a problem quite like this one. I have water damage at the bottom corners of my sliding patio door. I removed the inside side trim and peeled back the linoleum floor to see the extent of the damage. The ply at the corners is pretty shot but the studs above seem to be pristine. That indicated to me that the door/flashing/J-channel is not leaking around the top or sides. That maybe was not a correct conclusion, but it led me to do the following: On the sliding-door-side (opposed to the fixed-door-side), I plugged the drain hole with chewing gum and poured about half a cup of water in the bottom track. In about a minute, the water slowly drained down the corner where the track meets the side. Ah ha! Although the floor eventually got damp under that corner, most of the water came out on the floor on the opposite side. Hmm. (See attached pictures.) Bottom line, is the door defective and a manufacturing issue (the seal has failed at the sides)? Or is there supposed to be an underneath sill/flashing to capture that water and direct it outside (installed incorrectly)? Caulking the corners seems to be a temporary fix that will eventually fail. Am I even on the right track? Additional info that may or may not be important: The door is a Therma-Tru and my home was built by Ryan Homes 6 years ago. I installed a deck 5 years ago and flashed up underneath the door and over the deck ledger board. Deck is 2 inches below sill of door. The flashing also extends up under the side J-channels about 2 inches. (I am worried that I somehow caused this, but not sure how.) No deck or roof above door. I would appreciate any help or insight.