From the exterior, this clad round-top window looked to be in decent shape, trimmed with PVC that had been installed about five years earlier to replace the window’s original wood trim. But inside the house, the reason the wood trim had required replacement was obvious: The drywall underneath the window had water damage and water was leaking into the basement below. The problem could be traced to the location of the window, which had been retrofitted to the gable wall in a previous renovation. With virtually no roof overhang above to protect it and positioned beneath a lower roof that drains directly onto it, this round-top window provided a perfect entry point for rainwater, which was funneled off the roof-to-wall intersection onto the window. From there, it flowed off the round-top flashing, down the sides of the window casing and behind the shingle siding, and into the wall cavity. Still, had the carpenter who replaced the trim not cut through the WRB underneath the siding, I don’t think there would have been nearly as much moisture damage. Finding and fixing the existing problem was one of my goals, but I also wanted to do everything I could to prevent future problems with this window, which was clearly not in an ideal location.
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