Traditional Roof Valley Construction

In order to understand roof valley construction completely you need to know about the difference between an open roof valley and a closed roof.

Traditional roof valley construction.

A common misconception is that the mortar bedding is there to prevent water access. This is because the old valleys used to be galvanised and they start corroding with time especially if they trap leaves. If the roof valley which is going to be put in place is a closed valley then the person who is repairing your roof will place the roofing shingles on top of the roof deck. Essentially there are three main ways to shingle a roof valley.

One layer each of felt underlayment mineral surfaced roll roofing and two layers of shingles. Typically where a valley is located on a roof roof valley replacements are fairly common especially on tiled roofs. It is an area where water is directed towards rather than away from therefore correct detailing and construction is essential. Woven closed cut and open.

A closed cut roof valley will have at least four layers of roof materials. One of the areas of a pitched roof most prone to leakage if not constructed properly is the valley. Your choice of valley installation method is critical because when improperly installed valleys are risks for serious leaks. Valleys are typically found where gable dormer roofs meet the main roof or when a house has angled wings or additions where two roof sections in different planes meet.

The valley area of a roof the straight lines formed when two different planes of the roof meet is a critical area that handles a tremendous amount of water run off.