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What is Flashing?

What is Flashing?

What is Flashing?

The purpose of flashing

You may have heard the term “flashing” and be curious as to what that is. Flashing is essential for keeping water from the vulnerable areas of your roof. It is a layer of waterproof material that is placed over joints in the roof and protects valleys, chimneys, skylights and pipes. 

Things to remember about flashing

  • There are a variety of roof flashing products. Every single one has its own installation process. 
  • The roof flashing type that you need is based on the material of your roof, and personal preference. 
  • It is possible to do an at-home repair on flashing. However, this needs to be done with upmost confidence and necessary abilities. It should not be done alone if they are severely damaged. Always follow the manufacturer’s instructions closely.
  • Each flashing type has a unique way to install it. Some are installed before the shingles, and some are installed after. 
  • Generally, asphalt roofs either have a roll roofing or self-adhered membrane flashing while metal roofs use a standing-seam metal flashing. 

What is flashing made of?

Flashing is available in a number of different materials.
  • Aluminum: Aluminum flashing is a durable a cost-friendly option. It is important to note that it can wear down if it comes into contact with concrete or fiber cement siding.
  • Copper: Copper is harder to form than aluminum and most costly, but it is very durable. Also, it is compatible with newer wood type preservations used for roofing.
  • Lead: Lead is oftentimes used for chimney flashing for its ease of molding and bending. Another extremely durable option.
  • Galvanized steel: Along with a cheaper price tag, comes a less durable option of galvanized steel.
  • PVC: Finally, Polyvinyl Chloride is inert and easy to work with. 

Aspects of the home that require flashing

The following are areas on the roof that generally require flashing in order to protect your home from leaks which will save you from water damage repairs down the road. 
  • Dormer windows: Dormer windows are especially vulnerable to the elements because of the way the eject from the roof. Flashing squares are often placed between every row of roofing materials. It can also be used as a strip of flashing that runs around the dormer and under the roofing material. 
  • Skylights: When skylights are built into a roof, they are raised with a wooden curb to provide room for flashing material. If you are replacing your roof, you may need to raise the skylight to properly install flashing. Some skylights come with built in flashing, but these types of skylights could require additional flashing. 
  • Chimneys: Flashing strips are typically used on chimneys. These strips are usually made out of metal or PVC flashing and cover the joint between the chimney and the roof. The flashing is overlapped by the edge of the roofing material on one side and cap flashing on the other. The cap flashing attaches to the chimneys mortar joints. 
  • Vents: Vents are a necessary feature in any roof. If the vent is already installed, then the height of the flashing detail may need to be altered around the vent. There are two types of vents — hood vents and pipe vents. For hood vents, a flashing flange will have to be placed under the shingles above the vent. For pipe vents, flashing will need to be slid over the pipe once it is installed.
  • Valleys: If you have a sloped roof, then you need to add flashing to the valleys. The valleys where the two planes of a roof meet, are notorious for developing leaks. 


In conclusion, flashing is an essential roofing element that is yet another line of defense against water damage. Also, it is important that you choose the correct type and installation method for your roof’s specific needs. Be sure to follow the guidelines and directions carefully if you chose to install your own because this could be the difference of thousands of dollars in damage. 

Worried about a leaky roof? Check out this blog post.

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