Open Vs Closed Valley Roof

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.

Open vs closed valley roof.

This leaves a metal strip or line on the surface of the roof that serves as the valley line. Shingles are cut on the higher slope in a straight line through the valley. An open valley has a gap usually about 6 inches between the tile or shingles at the valley area. 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.

A closed valley is where the tiles or shingles are butted up against each other in the center of the valley. 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. I prefer open valleys to let the water run out on metal. Closed valleys may have a tendency if not constructed properly to channel water under the shingles laid over the bottom layer of shingles.

When compared to a closed valley and open valley adds an additional layer of lining. 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. Meanwhile on an open valley roof the metal lining that prevents water from seeping into the underlayers is left exposed. For an open valley a sheet of metal usually steel sometimes copper is fastened to the roof deck.

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. On a closed valley roof the shingles extend to the valley area completely closing it off. Once the shingles are installed they don t run through the valley area. 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.

With closed valleys the shingle life expectancy is shortened by water wearing away the valley shingles faster than those in the field.