Closed Vs Open Valley Roof

Although the open valley is recommended by the manufacturer closed valley is acceptable.

Closed vs open valley roof.

Proponents of the open version say that an open flashing allows the rainwater to move away from the roof faster. When compared to a closed valley and open valley adds an additional layer of lining. For an open valley a sheet of metal usually steel sometimes copper is fastened to the roof deck. 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.

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. I prefer open valleys to let the water run out on metal. 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. Closed roof valleys are also more affordable as installing a metal lining costs extra.

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. Closed valleys may have a tendency if not constructed properly to channel water under the shingles laid over the bottom layer of shingles. 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. 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. Shingles are cut on the higher slope in a straight line through the valley. On a closed valley roof the shingles extend to the valley area completely closing it off. It is always a good idea to check with the manufacturer or a certified installer of the product such as ourselves.

Meanwhile on an open valley roof the metal lining that prevents water from seeping into the underlayers is left exposed. 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.