What Is Roof Flashing?

2 min


Imagine when you were a kid and you would draw a house. Usually, you’d draw a square or rectangle for the inside and then put a triangle roof on top. Even as kids, we know that no house is complete without a roof. But there are a lot pieces that go into actual roofs, including things like shingles and flashing.

While most people know what shingles are, you may have never heard of the latter.

But roof flashing is just as essential to any roof system as the shingles, which is why we are going to explain everything you need to know about roof flashing.

What Is Roof Flashing?

You probably have seen roof flashing without realizing it. Flashing is thin material that can be made from plastics or metals and is used to help keep moisture from getting under the thin layers of shingles. You will usually find roof flashing along the sidewalls and headwalls of a roof. Chimneys also use flashing to keep moisture from getting in around the base.

Other features, like seams around windows and skylights require specialized flashing, since the shapes of these features can be unique.

Where Does Flashing Go?

Flashing has long been an integral part of any roofing system—one that has been utilized for centuries! Despite its use, roof flashing is overlooked. But if you don’t consider where it goes, then you might find yourself dealing with water damage and other issues.

Here are some places where you can find roof flashing:

  • Valleys: A valley is where two sloping sections of a roof meet. The shingles here do not overlap, so you install flashing to behave like a gutter.
  • Bases: This refers to things like front walls (headwalls). Flashing is installed in accordance to roof pitch and will often be overlaid with shingles and siding, depending on the location.
  • Steps: Flashing can be seen near sidewalls, because it is angled to match the roof pitch, right where the roof deck and sidewall meet.
  • Drip Edges: These are installed along the edges of the roof to direct water towards gutters.
  • Vents: These outlets need specialized flashing.
  • Chimneys: Another feature that requires customized flashing.
  • Skylights: Usually, when you install skylights, they come with their own flashing to add to the roof for leak prevention.

You will also hear roof flashing categorized by the places where it has been installed. For instance, flashing seen in valleys is called “valley flashing.” If you happen to have issues with your flashing and need a professional to repair your roof, be sure to use the location name!

How Long Does Flashing Last?

If you have a professional install flashing, then you can expect it to last for 15 to 40 years. Be sure to do routine maintenance on your roof to protect both the shingles and the roof flashing.


Roof flashing is something that every roof with a slope is going to have, regardless of the materials used for shingles. Flashing is also something that requires maintenance to remain functional. Now you know a bit more about your roof!

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