If you have a roof valley, it is important to install valley flashing. A roof valley is where two slopes meet. The flashing is installed above the felt before the shingles, but it can still be installed with existing shingles. If you need to complete this task, thankfully, you don't need advanced roofing skills to lay flashing, but you should feel comfortable working from heights. Here are some tips to install metal flashing in roof valleys.
For this project, you will need:
- work gloves
- extension ladder
- tape measure
- valley battens
- metal roofing nails
- roofing caulk
- caulk gun
- spray granules or wood pellets
- replacement shingles
- roof felt
- metal shears
- metal flashing
To start off, set an extension ladder on flat ground. Get an assistant to hold the ladder for you, or attach a safety harness on the opposite side of the work area.
Measure the roof span to determine how much flashing you need, adding several inches for overlap. Remove the nails in the shingles with the claw end of the hammer and save the nails. Then replace the roof felt.
Install the First Flashing Panel and Battens
Battens are plastic, wood, or metal square materials used as an installation point for roofing materials. Lay the battens on each end of the roof valley.
Secure the flange of the batten on the valley, leaving a slight overlap on the flange. Extend the flashing the same distance on fascia boards (the horizontal boards on the end of gutters). Overlapping the flashing protects the roof valley from ice dams.
Set the first sheet of flashing at the lower end of the valley on the top flange of the batten with the flashing overlapping an inch over the flange. Trim the sheets to fit with the shears as needed. Apply a bead of caulk around the underside of the upper flange edge, and press the flashing down on the caulk to secure it.
If you feel the caulking isn't enough to secure the flashing, hammer in metal roofing nails at an angle, one on each side around an inch from the flashing edges. Fill nail holes with caulk.
Lay the Rest of the Flashing
Install the remaining flashing in the same manner, leaving an overlap of several inches on each piece. Trim the pieces as needed. Hammer another nail in the top of the flashing after you trim it. Then you can add a layer of granule or wood pellets to the cut edges of the flashing for rust prevention. Fill the spaces between flashing with caulk. Reinstall the shingles.
Your roof will last longer with metal roof valley flashing. If your roof is very high, you don't trust your skill, or you think it's time for a new roof, contact a roof installation expert.