Open Vs Closed Valley Roof

A closed valley is where the tiles or shingles are butted up against each other in the center of the valley.

Open vs closed valley roof.

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. Meanwhile on an open valley roof the metal lining that prevents water from seeping into the underlayers is left exposed. Once the shingles are installed they don t run through the valley area. Closed valleys may have a tendency if not constructed properly to channel water under the shingles laid over the bottom layer of shingles.

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. I prefer open valleys to let the water run out on metal. When compared to a closed valley and open valley adds an additional layer of lining.

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. 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. 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.

With closed valleys the shingle life expectancy is shortened by water wearing away the valley shingles faster than those in the field. This leaves a metal strip or line on the surface of the roof that serves as the valley line. 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. Closed valleys are very vulnerable to mechanical damage.

The metal is usually pre painted to best complement the shingles color blend.