There are two methods for sealing valleys.
Open vs closed valley roof.
According to long time iko sales representative jeff tessaro closed valleys for residential construction have been popular since he was a roofing contractor in the late 90 s.
With each new course roofing shingles continue up the valley.
Furthermore the description of the roofing company whose closed valley failed seemed to fit the profile of a fly by night roofing company and so i d have to assume that workmanship and expertise was secondary to making a quick buck.
A closed valley is where the tiles or shingles are butted up against each other in the center of the valley.
Moving on here are a couple of things to think about when deciding open or closed.
Find out the differences before you talk to a roofing expert.
What is an open valley roof.
For a closed valley shingles are installed across the joint where planes intersect.
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.
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.
After the self adhering underlayment is installed across the valley a pre bent metal valley lining is installed.
An open valley has a gap usually about 6 inches between the tile or shingles at the valley area.
Because of the sheer amount of water being navigated through this section your valleys need to be properly sealed.