open valleys on shingled roof

[billconner]

I've done open valleys with galvanized W valley flashing before. Shingles run to within 2 to 3 inches of center, trimmed parallel to center, and top corners clipped.

Googling, I see laying full shingles parallel to valley, end to end, **** 2 to 3 inches from center, and then whole shingles laid so corner is on edge of parallel.

Anyone can speak to this "new" approach?

 

[Rusted Nut]

Wouldn’t call it a new approach, been in use for years. Valleys can be done with metal flashing, woven, or the new approach. They all work, really a matter of appearance. Personally I think woven is the best, as far as leakproof, but only works on roofs up about 8/12 pitch.

 

[billconner]

Well, I always prefer the open W valley as being self cleaning, especially at low slope. This is 3:12. Also almost impossible to see except from bedroom window over it since it's at top of hill. But I was comparing just two ways to do an open valley with W flashing. This requires no cuts.

Starts around 3:40.

 

[firebirdparts]

requires no cuts, is uglier, and has an adhesive strip running along the flashing. I guess I will offer that I don't like it. I am glad he figured out he was nailing it wrong. I was pretty horrified when I started watching it.

 

[billconner]

It's interesting. Easy. No or less horizontal edges to catch and divert water. But only single coverage in those "triangles". Still better than woven or closed cut IMHO.

I'll probably do the traditional open valley with clipped corners, and a heavy bead of touch cement along the edge of the metal.

 

[Beauregard]

I always had problems getting open valleys to seal, especially with 18" of wet snow slowly melting sitting in them. Water seemed to seep under the shingles. Weaving the valleys solved the problem.