So, I had some water damage in my trunk and for the longest time thought it was the wing on my trunk leaking. Turns out I had 1" of water in the wheel well. Finally decided to fix the problem. This is being done on my 2004 Subaru WRX.
Things to do before: Make sure you locate the source of the water. In my case it was water under the carpet. However your issue maybe bigger than this.
-Heater (to ensure all cracks are dried)
- 4' x 4' x 1/4" plywood - $12
- 4' x 6' Carpet - $12
(All from Lowe's)