Open Cut Roof Valley

See our discussion of alternative flashing materials found.

Open cut roof valley.

Roof is 5 12 slope with a couple of valleys. I m trying to decide on the best way to do the valleys open metal valleys or closed cut ones. Roofing shingles are installed then cut and sealed where they overlap the metal channel. A roof using the open valley style involves placing a v or w shaped piece of metal usually galvanized or sometimes copper in the seam of the valley and then covered with a base sheet such as 30lb.

I want my roof to be as leak proof and long lasting as possible. With sheet metal protecting the lower layer of shingles the shingles on top are cut back to the line right. In this video i show you how i do the valleys on a shingle roof. The shingles are then cut out of the valley area opening the surface of the valley lining to water run off and the environment.

When all the shingles are installed to the guide line the cutline is resnapped left. At flashing wall details. The seam where the two planes of roofing meet are aesthetically woven together to form an interlaced design which creates a seam that matches the contours of the roof. That flashing is left exposed so the roof has visible lines of metal running down the valley.

One nail goes into the top section of the shingle where it covers the valley metal. I m in a mixed humid climate zone 4a. Can t afford standing seam metal though so it will be mid grade architectural asphalt shingles installed with meticulous detail. With a heavy gauge noncorrosive metal lining open valleys are the most durable valley and the most costly.

A chalk line is then used to strike a line from the top of the valley to the bottom of the valley. With an open valley a strip of metal will be visible on the roof wherever two opposing roof planes meet. No one of this affirmat. The cut edge then is sealed with roof cement.

Open valleys may be susceptible to water backup if the cut off shingles are not properly trimmed potentially causing roof leaks. An open valley relies on metal flashing for protection. However it is said that provided the rest of the roofing shingles were properly installed and are performing properly open valleys will perform better over time than closed valleys. An economical version uses two layers of roll roofing for the lining which should last as long as an asphalt roof.

I finish the cut edge with a double bead of roof cement the same as for the open metal valley. Some homeowners do not like the look of open valleys while others feel the metal accentuates the roof s shape particularly if copper or painted flashing is used. Many roofers cut the shingles across because they say it s safer. For an open valley a sheet of metal usually steel sometimes copper is fastened to the roof deck.

Open valley shingle installation. And either an organic or modified underlayment depending on whether tiles or shingles are being.