I have a two sided metal roof with a different grade on each side. The two sides do not meet at the center. The design incorporated vertical sky windows in the center of the roof which creates a hip joint that is only met by the steeper side of the roof. Therein lies rain leaks after years of neglect. Anyway, the original builder did not address the joints where the lower grade side meets the sky windows. They simply just left bare wood and a cavity on each side. The cavities are allowing tons of rain to get in.
Keep in mind that here in South Carolina we get severe winds and rain.
I have come up with possible solutions, but my ideas have inherent flaws. I have 10" x 10' of flashing to use and after searching the local home improvement store it seems flashing is my only choice. I want a solution that is permanent. If there was a product designed for situations like this, I'd go for that, but I have yet to find any.
Just bending some flashing around the corner seems great, but then I have vertical edges on the flashing to worry about. Furthermore, the exterior side panels are popping out about a half inch up to an inch all the way from the joint to the steeper roof side. So even with the flashing bent around the corner, rain can still get behind.
To further complicate the situation, the metal sheeting on the lower grade protrudes out from the edge about a foot and needs flashing as well to prevent rain from getting underneath. I was planning on sealing the flashing with caulking, but underneath the flashing for better results and to protect the caulking from the sun.
Please do not recommend relying solely on a sealant.