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What Is Flashing Tape?

Updated February 21, 2017

The invention of flashing tape has done much to simplify a wide range of building projects. This strong, waterproof adhesive is used during construction to tightly seal off the gaps between windows/doors and the exterior of the house. Many roofers also use flashing tape to seal cracks before securing shingles.

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Flashing tape is composed of a durable strip of thin aluminium (or other similar substance) with a thick, highly adhesive backing that conforms to the structure surrounding it. It is available from a variety of vendors in sizes that range from 5cm to 60cm. Flashing tape is available in red, blue, silver and white, among other colours.

What It Replaced

Before flashing tape was available, builders filled the spaces formed when installing windows and doors with heavy duty caulking. However, over time caulk becomes dried out and cracked, allowing moisture to enter the building and increasing the likelihood of mould growth. Windows and doors sealed with caulk also allow temperatures from the outside to enter the house, reducing energy efficiency and raising the cost of power bills.


Flashing tape is available in lightweight, convenient rolls that are easy to store and dispense from. It provides a quick, no-mess sealant that is resistant to punctures and other damages. In addition to working to seal doors, windows and roofs, it is also commonly used around vents, chimneys, skylights and other fixtures that project through the exterior of the building.


While flashing tape is resistant to the damage of UV rays, it should not be left exposed for more than 30 days. In fact, many builders recommend that the exterior covering be completed on the same day flashing is applied. It will not adhere well to surfaces containing polysulfide. It also should not be applied in the rain or when temperatures are below 4.44 degrees Celsius.

How to Use

When applying flashing tape, always seal the bottom of the window (or other opening) first by running a horizontal strip of tape from one end to the other. Then seal both sides, applying the tape from the top to the bottom and allowing it to overlap the tape at the bottom. Finally, seal the top of the opening tightly with another horizontal strip of tape. Be sure the top strip of tape extends an extra few inches in both directions so that water will be directed away from the opening.

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About the Author

Tiffany Bennett

Tiffany Bennett is a recent graduate from Toccoa Falls College. While earning her degree in counseling and psychology, she discovered that she enjoys various forms of writing. She is currently living in Athens, Ga., and looking forward to beginning a graduate degree program in international affairs at the University of Georgia.

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