Install Metal Flashing On a Roof Valley

Lead Image
  • 1-2 hours
  • Beginner
  • 30-150
What You'll Need
Metal roof valley flashing
Metal-cutting shears
Galvanized roofing nails
Sturdy extension ladder

Installing metal flashing for your roof project is a challenging but essential step to take to ensure that the new roof remains as weatherproof and as strong as possible. The following steps will explain how to install metal flashing in roof valleys. Flashing should be installed in all of the valleys. Roof valleys are where two faces of the roof meet, which will be the case in any gable or hip-roof that has multiple roof sections. For those who have a basic level of knowledge and experience with roofing, the following steps should be fairly straightforward to complete.

Step 1 – Make Preparations

Before you purchase the roof valley flashing, determine how much you will need. Purchase a little bit extra to allow room for adjustments. To determine the quantity that you need, measure the length of the valley, adding an extra six inches just to be on the safe side. It is also a good idea to have someone help you by holding the ladder and passing up tools and materials as needed.

Step 2 – Place the Flashing on the Roof

Lay the flashing down in the roof valley and start at the lower end of the roof. Make sure that the end of the flashing panel is perfectly in line with the edge of the roof. Attach the flashing panel in place at the bottom. Use 1-inch galvanized roofing nails. To begin with, place a nail on each side of the bottom of the flashing panel about 1 inch from both sides of the corners. Use a hammer that is suitable for working on the roof.

Step 3 – Attach the Flashing in Place

Work your way up the roof, attaching the flashing in place with the roofing nails as you go. Place the roofing screws every six inches. Once you get towards the top of the roof, do not nail the top edge to the roof just yet.

Step 4 – Install the Second Flashing Panel

Install the second flashing panel, allowing it to overlap the one that you have just installed by about 2 inches. Attach the flashing panel in place in the same manner as you did with the previous one, placing roofing nails every six inches. As before, make sure that the bottom end is flush with the bottom of the roof. Make sure that the lower nails run through each of the flashing panels.

Step 5 – Trim the End of the Flashing

You may need to trim off the end of the flashing a little. Climb up to the top of the roof, and trim any excess flashing off using a sharp set of tin snips* that are specifically designed to cut metal. Finally, nail down the top of the flashing after you have cut away any excess. Now that you are finished, the roof should last for many years with minimal maintenance.

* Pro Tip: The handles of all tin snips are color-coded. Yellow is for making straight cuts while Green is for left-hand cuts and red is for right-hand cuts. For left cuts, the scrap will be on the right and for the right cuts, the scrap will be on the left. Off-set tin snips help keep your hands away from sharp metal edges as you cut it.