Waterproofing the Rear!

Well, for once I am taking advice I usually give to new homeowners... take care of the roof and exterior maintenance before working on the interior. We have had a lot of rain these first few weeks of spring but a sunny (2-days-in-row) and "no" client work in my work room coincided today so I devoted the day to problem solving, cleaning, and sealing the exterior trim on the rear end of the '65 Tradewind. The front window doesn't seam too bad as it has an extra rock guard covering. In the rear, from the inside of the trailer, I could see moisture on the upper corner of the back window. The plywood floor has also been very moist. I was planning to tackle the new water lines but I changed gears and heard my own voice saying to take care of the roof before getting to the interior! I did some crowd sourcing for advice and although everyone seams to have their own favorite product, the hot tip of the day was to clean the aluminum with rubbing alcohol and use a finger dipped ...