How To Install Metal Roof Valley Flashing

If you are installing a roof flashing, you will eventually come to a valley. Roof valleys are where two faces of the roof meet. Installing flashing in this area will help weatherproof the area, and make the roof last longer.

Installing flashing should be no problem for anyone with some DIY skills. Here are tips to install roof valley flashing.

Prepare to Work

For this project, you will need:

  • ladder or scaffold
  • work gloves
  • hammer
  • galvanized roofing nails
  • roofing cement
  • roofing paper
  • caulking
  • trowel
  • metal cutting shears
  • metal flashing

Try to work when there will be several days of sun. Set a ladder on flat ground. A scaffold is ideal for high roofs.

For extra safety, use a safety harness tied to opposite the work area. Get an assistant to hold the ladder and hand you tools, or wear a tool belt. Wear rubber-sole shoes for good traction.

Measure the roof valley with a tape measure to figure how much flashing you will need, and add an extra six inches. Don't try to guess measurements.

Lay the First Flashing Panel

Start laying the flashing from the bottom. Lay a piece of flashing in the valley seam to fit the length.

Trim the flashing with metal shears to fit around eaves and the ridge. Spread some roofing cement along the exterior edges from the bottom to top. Set the flashing in place.

Drive in a nail an inch from the panel edges.You may also attach the panels with an electric screw gun and screws. Place nails or screw six inches apart. Take care not to nail too far into the roofing below.

Spacing for nails and screws differs depending on panel size. Most flashing panels have a common center spacing of sixteen inches.

Roll out roofing paper over the flashing. Trim roofing paper to fit the distance between the eaves and roof edge. Nail it in place over the flashing.

Install Additional Panels

Install the second panel to face the roof ridge; overlapping it on the first panel about four inches. Overlapping the panels prevents gap, where water can enter.

Pour some roofing cement in a trowel. Spread on roofing cement and, nail the panel down in the same manner as the first panel.

Trim off excess flashing with the metal shears, and secure it. Fill in gaps and nail holes with roof caulking.  

You are now ready to install the shingles. Roof flashing adds an aesthetic appeal as well as prevents damage. If you don't trust your skill, or the roof is seriously damaged, it may be in your interest to contact a roofing contractor.