A homeowner recently contacted me about repairing some siding on his house. That work led to a discussion about his box bay window, which a contractor had installed about 10 years before. Though the clad Andersen windows in the box bay appeared to be in good shape, my client explained that they were difficult to open and close and that he had noticed some water leakage on the interior.
Based on experience, I suspected that the leakage problem was worse than it appeared. My hunch was confirmed as I started pulling off the interior and exterior trim to look at the framing. On the interior, water stains were visible above and below the windows, and when I removed the windows’ stool, it looked like mice and ants had taken up residence in the space between the stool and the subsill—never a good sign. Still, the worst of the damage remained largely hidden until I started removing the exterior trim and uncovered extensive rot in the 2x12s that had been added to the rough opening in the home’s 2x6 wall to create the box bay.
The box-bay framing had a number of problems, such as a lack of sheathing, inadequate flashing, and no structural support for the 2x12 subsill other than the 2x6 wall that it was resting on. But the main problem was that water from the roof flowed down the fascia and behind the exterior head casing used to trim the windows. From there, it worked its way down the 2x4 jack studs separating the windows and collected on the 2x12 subsill. As a result, the subsill was rotted and split, and the bottoms of the 2x4 studs were rotted. At both sides of the opening, the 2x12 trimmers had virtually disintegrated, so once I removed the trim, nothing was holding the windows in place.Read More