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A roof valley is formed where two sloping roof areas intersect to create an internal roof channel that drains run-off water from higher roof sections. The valley is one of the most critical details on the roof because it collects a lot of water. An improper installed valley can be the cause of serious leaks.

Essentially, there are three main ways to shingle a roof valley: woven, closed-cut and open. There are various techniques you’ll need to know for each type of installation, which will be explained in this blog. Before you decide how to shingle a roof valley, you will need to consider your materials, the climate and the desired look of the roof.

Preparation of the valley with an underlayment is a critical part of your roof installation. The underlayment is an integral part of every valley and provides a waterproof base. All valley installations require appropriate underlayment layers. We recommend using our IKO Armourbase range of underlays, which are very durable polyester membranes on bituminous base. Valley underlayment sheets should be centered in the valley and secured with only enough fasteners to hold them in place until the primary valley installation is complete. Self-adhesive IKO Armourbase Stick underlayment may not require too much fastening. The underlayment material from the two adjacent roof planes should overlap the valley base sheet by at least 15 cm. Also all the fasteners should be kept a minimum of 15 cm from the valley's center line.