An open valley is one of the most common valleys used in slate roofing in which the chosen flashing material is exposed.
After the underlayment is installed across the valley, the flashing is installed providing an additional layer of lining.
Open valleys are advantageous in locations where foliage accumulates and they also shed ice and water more quickly.
The slate is installed a minimum of 3 to 4 inches each side of the valley centerline. Installed with a taper which increases from top to bottom.
When installing a valley, make sure its straight!