What Is Roof Flashing?

What Is Roof Flashing?

When you look at your roof, you probably see shingles, clay tiles or other materials designed to safeguard your property from inclement weather. The roof over your head keeps your home safe and dry. However, it’s one of the less-known materials that works the hardest to keep water and moisture from invading your house — the roof flashing. What is roof flashing? It’s the unsung hero that prevents leaks on your roof — or not. Roof flashing details include size and materials. Learn more about roof flashing here.

About Roof Flashing

Roof flashing is thin material, usually made of metal, that directs water from vulnerable areas of the roof. Professional roofers install it around chimneys, vents and skylights. Here’s how it works: Water runs down the flashing to the shingles instead of into exposed seams, including where vents poke through the roof deck.

Improperly installed flashing causes numerous problems. For example, improperly installed chimney flashing can cause water to run down the side of the chimney and affect the joists and rafters underneath.

Types of Roof Flashing

What is roof flashing used for? Before choosing the material and size for particular roof flashing jobs, consider the different ways you can use it to protect vulnerable areas on the roof.

  • Continuous flashing: This type of flashing gets installed in one long piece to protect the joint between a sloped roof and a vertical wall.
  • Drip edges: You can find drip edge flashing along the eaves. Roofers install it beneath the roofing felt to keep run-off water from seeping under it.
  • Step flashing: Shaped to fit the joint of a roof and fixture. These overlapped flashings prevent water from getting behind them.
  • Valley flashing: Open valleys between roof planes are protected by valley flashing installed on top of the roofing felt.
  • Vent pipe flashing: A cone-shaped fitting for pipes that are worked into the shingles for continuity.
  • Saddle flashing: Covers railing attachments and beams. Roofers need to be familiar with the appropriate building codes regulating saddle flashing.
  • Cap flashing: An L-shaped structure between the roof and windows or other structures. The shape prevents water from pooling in any cracks where structures meet.

Roof Flashing Details

According to the NACHI, flashing needs to fit the application. Roof flashing details are a key factor in proper installation. Different parts of the roof require specific roof flashing sizes and materials.


The NRCA recommends minimum metal thickness for specific configurations, based on the roof type. Also, the dimensions of the flashing must match the purpose. Here are two examples:

  • Roofers make the flashing for your plumbing vent large enough to go around the vent. It should be somewhat wider than the diameter of the vent.
  • Step flashing pieces are 10 inches long and 2 inches wider than the shingle exposure. For example, three-tab shingles have a visible area of 5 5/8-inch. Typically, 10- by 8-inch flashing works well for these shingles.


Roof Flashing Materials

What is roof flashing material? Although plastic and roofing felt can be used for flashing, most applications require metal material for durability and effectiveness.

  • Plastic: Plastic or PVC provides waterproof protection. However, PVC doesn’t work with asphalt, making it unsuitable for many roofs.
  • Roofing felt: Felt can be used with other material for flashing. By itself, it doesn’t provide full waterproof protection.
  • Rubber: Rubber is not recommended. It’s flammable and weakens and tears over time.
  • Galvanized steel: Steel lasts a long time and is extremely durable. This is a cost-effective choice for flashing since it is also rust-proof.
  • Aluminum: Flexible aluminum flashing bends with little force. It works well on oddly shaped roof features.
  • Copper: Copper flashing is customized to match copper roofing.


Contact Us Today for Your Roofing Needs

Thompson Creek Window Company can help you ensure that your new or existing roof has the appropriate roof flashing details to keep your home snug and dry. Contact Thompson Creek for all your window and roofing needs. We’ll be happy to answer your questions about your next roofing project.