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A Brief Lesson in Roof Flashing


A Brief Lesson in Roof Flashing

If you’re replacing a roof, or maybe your contractor is just working on some repairs, you can’t forget about flashing.

What is Flashing?

Water is the enemy of most construction, including your house, deck, shed, porch, and so on. If water gets into where it doesn’t belong and stays there, then it can do some serious damage. In order to prevent water from getting into places that shouldn’t, a contractor will install flashing. Areas such as vents, windows, and junctions are all areas where you might see flashing on a roof. It is placed beneath the outermost surface for the majority of the job and may have a little that runs over the top to account for runoff. The materials used for flashing can vary between sheet metal, plastic, and composite materials. Proper flashing can prevent significant water damage from entering into your home and increase the lifespan of the materials. However, if you’re replacing your roof by placing it on top of your existing one, it will cut the life by 20% according to experts, and so flashing will only be a temporary benefit.


There are a few different styles of vents that vary in shape and size, although they will all still need flashing. The two most common styles are hood vents and pipe vents.

  • Hood Vents: These are the flat, shorter vents that are usually circular in shape. The flashing flange will be set underneath the shingles above the vent, but over the shingles below the vent. All the joints will need to be sealed once the flange is in place and the vent cap placed back on the vent.
  • Pipe Vents: These vents are essentially cylindrical pipes that jut out from the surface. In this case, pipe flashing will need to be placed over the top of the pipe and fan out at the bottom, like a cone. The bottom part of the flashing will extend over the top of the shingles like the flashing for hood vents.


Flashing will be needed for windows that extend out from a vertical slope, also known as dormers. Flashing strips are usually placed beneath the outer layer of material and around the base of the dormer. However, flashing squares can also be used and placed between each row of shingles as well. The only difference between the flashing on a dormer and that on a regular window is that a dormer typically gets an apron. An apron is just a large section of flashing that is placed in front of the window and over the materials so that water can run downward without restriction.

When tackling a project such as this, you’ll want to consult with the experts. Improper or non-existent installation can cause significant damage to your home and a lot more money than you think you saved by doing it yourself.

For a professional roofing service, contact Pro Home Services today.





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