I have to box in some pipes on my flat roof, since there is no way I can properly flash around the soil pipes going through the roof/bathroom wall etc, since it is very close to the wall and has a side connector for the toilet and bathroom sink. The guys at a local roofing company confirmed this is what they would do. I intend to box in using plywood/felt so it blends in with the roof. So I have 3D external corners to felt over. This could be done by folding the corners, but with a 3-layer felting they would end up very messy. What is the best way to cover these corners, and the similar situation where the box corners meet the roof ? Simon.