Open Vs Closed Valley Roof

For an open valley a sheet of metal usually steel sometimes copper is fastened to the roof deck.

Open vs closed valley roof.

An open valley has a gap usually about 6 inches between the tile or shingles at the valley area. The metal is usually pre painted to best complement the shingles color blend. 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.

This leaves a metal strip or line on the surface of the roof that serves as the valley line. Closed valleys are very vulnerable to mechanical damage. 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. Shingles are cut on the higher slope in a straight line through the valley. 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. 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. 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. Closed valleys may have a tendency if not constructed properly to channel water under the shingles laid over the bottom layer of shingles.

I prefer open valleys to let the water run out on metal.