I did a complete rebuild of my cabover and the leak areas were at a roof angle transition and a seam that runs across the roof. The seam leaked on both sides of the RV and the cabover floor was rotting on both sides.
When I put it all together, I sealed with a combination of Eternabond on edges and butyl tape under the metal trim strips that cover the actual seam. The next area to worry about is window frames. The last thing to make sure you check is the actual glass of the windows.
I am for sure going to make a pressurizing rig and test my RV in the spring.
Jose
