Your choice of valley installation method is critical because when improperly installed valleys are risks for serious leaks.
Roof valley pointing.
After about a year the pointing from one of the valleys fell out.
Sheathing blocking is added along the valley and the sheathing pieced in for both roof planes.
I suspect it has never been done properly each of the 3 times it has been pointed.
I have loose mortar to two valleys either side of a gable built as an extension eight years ago.
A scaffold tower has been used for access in this video.
Using clips permits movement in the valley as temperatures change.
The original roof ridges and pointing built 1990 are fine but the pointing in the more recent valleys is crumbling and falling into gutters.
This is how i cement roof tiles pointing the verge in with two coats of cement the cement i use has black dye mix in it to help match the roof tiles in colo.
Water collects in a valley to flow off the roof.
I had my roof retiled about 6 years ago.
Use roof valley cleats at intervals of 24 o c.
A roof valley is formed where two roof slopes meet.
A roof valley is very prone to leaks especially if you have an older roof.
Essentially there are three main ways to shingle a roof valley.
To transition the eaves the horizontal fascia extends to the last rafter tail and a vertical return finishes the transition.
This video shows how to repoint a lead roof valley.
I had it repointed but it fell out again after another year.
Woven closed cut and open.
I had it repointed again in october 2014 and it has fallen out again from under the roof tiles.
The reason why the roof valley is such a sensitive area has to do with all the rainwater and or melting snow that accumulates and flows through the valley on its way into the gutters.
The installer fabricates simple clips or valley flashing cleats whose bent edge interlocks with the folded over or hemmed edges of the metal roof valley flashing to secure the valley to the roof deck.
At the low end of the valley the subfascias of the two roofs are mitered with a block filling in the roof framing.