I have installed a new shed in my back yard. I am, by no means, qualified as a roofer. The roof came out pretty good. It is a barn style roof, with 2 haunches. There is a section on the roof where it looks sunken right before the second haunch location. Water collects here and a small leak appears when it rains. What can I do, aside from re-roofing that side, to clear up this issue?