Closed Vs Open Valley Roof

It is always a good idea to check with the manufacturer or a certified installer of the product such as ourselves.

Closed vs open valley roof.

This allows water to fall from the higher slope to the lower slope and prevents it from going under the shingles to the roof deck. Closed valleys may have a tendency if not constructed properly to channel water under the shingles laid over the bottom layer of shingles. Meanwhile on an open valley roof the metal lining that prevents water from seeping into the underlayers is left exposed. Thus closed roof valleys extend the time between your roof repair projects.

The metal is usually pre painted to best complement the shingles color blend. The closed variation is a flashing that has been completely covered with shingles while in the open variation will have the flashing completely exposed to the elements. With closed valleys the shingle life expectancy is shortened by water wearing away the valley shingles faster than those in the field. Closed roof valleys are also more affordable as installing a metal lining costs extra.

Since it isn t bogged down by the friction shingles invariably create. That said an open roof valley is a good option if you want to the metal strip to serve as an architectural detail on the roof. Shingles are cut on the higher slope in a straight line through the valley. And while some homeowners may prefer the aesthetics of a closed valley the heavier and thicker the shingle the less likely it is to lie flat across a joint.

However open valleys may be susceptible to water back up along the top of the cut off shingles in the valley if not properly trimmed potentially causing roof leaks. For an open valley a sheet of metal usually steel sometimes copper is fastened to the roof deck. On a closed valley roof the shingles extend to the valley area completely closing it off. The only type of valley that is unacceptable is the woven valley.

When you research this topic online you will likely find people who prefer one of these methods of the other and they will give their reason. Proponents of the open version say that an open flashing allows the rainwater to move away from the roof faster.