How can I tell if my valley flashings are installed properly?

expert EXPERT April 26, 2007

The best spot from which to examineyour valley flashing is at the eaves. From this vantage, you can sometimes see the following:

• the presence or absence of a base layer
• where the nails occur (preferably just at the outside edges)
• whether the valley flashing runs the full length
• the width of the flashing material
• whether metal valley flashings have returns and cleats at the edges
• whether the shingles were nailed through the valley or cemented in place

As with most roofing issues, the implications of any of these problems are roof leakage and damage to finishes and the structure below. Look at valley flashings from top to bottom for damage resulting from the installation problems described above. Look from below (in the attic and the interior of the home) to get an even better idea of the scope of the problem.

Don't forget to check dormer valleys. Flashing dormer valleys is a tricky process. On the main roof side of the valley, the bottom of the valley should have a row of shingles below, so water will shed onto the roof and run down rather than into the roofing system.

Never walk up roll roofing valleys. Since the roll roofing doesn't sit tightly against the sheathing in the valley, it is easy to put your foot through a valley flashing.