A roof valley is when 2 roof planes meet at an inside corner. Water runs down the intersecting roof planes, collects in the valley, and runs off the roof. Roof valleys are one of the most vulnerable parts of a roof due to the volume of water and debris that collects in roof valleys. Therefore, roof valleys should be treated with great care during and after the installation of the roof. Roof valleys should also be cleared free of debri such as oak tree leaves and pine needles as the debris soaks up the water and blocks the drainage potentially causing leaks and accelarates the deterioration of the roof covering prematurely.
