Open Vs Closed Valley Roof

Closed valleys may have a tendency if not constructed properly to channel water under the shingles laid over the bottom layer of shingles.

Open vs closed valley roof.

On a closed valley roof the shingles extend to the valley area completely closing it off. 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. Open roof valley this is almost the same as the closed roof valley method except a pre bent metal valley lining is installed instead of a secondary roof underlayment.

Shingles are cut on the higher slope in a straight line through the valley. Meanwhile on an open valley roof the metal lining that prevents water from seeping into the underlayers is left exposed. With closed valleys the shingle life expectancy is shortened by water wearing away the valley shingles faster than those in the field. If you have a shingled roof as most torontonians with a sloped roof tend to have then you will have one of two kinds of valleys on your home.

An open valley has a gap usually about 6 inches between the tile or shingles at the valley area. I prefer open valleys to let the water run out on metal. 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. Once the shingles are installed they don t run through the valley area.

Repairs to closed valleys are a lot more involved than working on an open valley as is re roofing or making changes to a portion of your roof in the future. 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. This leaves a metal strip or line on the surface of the roof that serves as the valley line. The metal is usually pre painted to best complement the shingles color blend.

Closed valleys are very vulnerable to mechanical damage.