How To Install A Metal Roof Valley Flashing

Attach the flashing panel in place at the bottom.

How to install a metal roof valley flashing.

First clean the debris out of the valley including sawdust nails and whatever else is in there. Lay the flashing down in the roof valley and start at the lower end of the roof. Shingle the other side of the valley the same way. Install synthetic roofing underlayment or felt paper according to manufacturer specifications and then install the first piece of valley flashing.

Low slope roofs slope less than 3 12 use tape sealant between the valley trim and the panel. Fold the top over the roof ridge and cut the bottom along the drip edge metal. With a clean valley you can lay down some peel and stick roofing membrane. Stop nailing 6 inches from the center.

Snap a chalkline 2 to 3 inches past the valley center on the top layer of shingles. Use 1 inch galvanized roofing nails. Then install a non corrosive metal valley flashing of 24 minimum width lap successive sheets of metal flashing a minimum of 12 inches and seal laps. Use fasteners to attach the panel to the structure making sure that there is complete compression of the sealant.

I have my valley custom made with water trough to help with leaking b. Best practices for sealing the metal roof valley vary based on the slope of the roof. Install an underlayment centered in the roof valley. Apply an approximately 3 inch width of asphalt roofing cement along the sides of flashing and embed shingles in mastic.

The top joinery of both valleys when they meet on the same plane of roof is shown here.