How to Attach Vertical Flashing

Examine your roof to determine the areas of the roof that will need vertical flashing. Ideally, you need to install this type of flashing anywhere that you have a vertical wall intersecting the surface of the roof. Any dormers need a special form of vertical flashing known as step flashing, while other ares of the roof, such as around a skylight, just need a straightforward installation.

Measure the length of the edges formed by the intersection of your roof and the other part of the house you will install flashing around.

Pull back the layers of roofing next to each vertical wall you intend to protect. Peel back each shingle gently to expose the underlayment. Place an additional piece of roofing felt alongside the edge of the vertical wall. Cut each piece so the felt paper is at least 7 inches wide. When you lay it down, 4 inches should lay on the roof and 3 inches should be up against the wall.

Remove any siding along that wall that you are installing the flashing against.

Cut each piece of metal flashing to the proper length using metal snips. The flashing should be bent so at least 3 inches of the flashing can lay up against each vertical wall. Bend each piece to slightly more than 90 degrees. You can do this by placing the flashing alongside the wall and creasing it gently. Do not push the seam all the way down. You want the flashing angle to be slightly more than 90 degrees so the crease sits out a fraction of an inch from the seam between the roof and the wall you are protecting.

Nail the flashing at each corner on the roof's with galvanized roofing nails. This should only take two nails.

Caulk around the edges of the flashing that lay on the roof. Use a silicone caulk. Also caulk around the nail holes to ensure that you haven't created any unwanted openings.

Lay the roofing shingles back in place and nail them in using the same type of roofing nails. You should now have a flattened roof with a 3-inch-wide piece of vertical flashing extending the length of the vertical wall.

Nail the upper corners of the flashing into the wall if you have a home with siding. When you are installing against a brick wall, you need to add brick mortar around the edges of the flashing to hold it in place.

Add a layer of caulk around the edges of the vertical flashing piece to seal it to the wall. Reattach your siding, if you had to remove it before installing the flashing.