Roof Flashing: What It is and How It Works – The Ultimate Guide

This guide answers some of the most frequently asked questions homeowners have about roof flashing. Whether you are tackling a complete re-roofing job, or simply need to repair the existing flashing on a leaky roof, this guide will help you find the right information in no time!

End-wall copper flashing on an asphalt shingle roof
via: Runyon and Sons Roofing

Table of contents:

Here is a quick table of contents to help you quickly find the right information.

  1. What Is a Roof flashing and Why Is It Important?
  2. Types of Flashing
  3. Roof Material Expenses (i.e., the cost of flashing and roof feature repair costs)
  4. Signs of Roof Flashing Failure
  5. How to Repair Roof Flashing
  6. Can Roof Flashing Be a DIY Project?

What Is a Roof Flashing and Why Is It Important?

While roofs are purposely constructed to allow rainwater run-off, they can often have several vertical features or protrusions, such as chimneys, parapet walls, half walls, dormers, skylights, vent pipes, and the like, where water can pool up and/or drip into the crevices between. The areas can eventually become damaged and allow water seepage and leaks into the house. To prevent this, professional roofers apply roof flashing to divert rainwater down the sides of the vertical surfaces, keeping the water from stagnating.

Roof flashing is typically a thin metal material fabricated from rust-resistant metal, such as G-90 galvanized steel, a frequently used flashing material, copper, or aluminum. Depending on the company, flashing may even be available in lead or zinc alloy.

Steel, copper, and aluminum are particularly used because of how malleable these metals are, rendering them easier to shape. However, the homeowner should note the different characteristics of each metal:

  • Galvanized steel is less costly than aluminum and copper, and is well resistant to corrosion. It is for these reasons that steel is most often chosen for flashing.
  • Copper is quite durable, but it discolors into a patina over time. Some homeowners appreciate the classic appearance of copper with patina.
  • Aluminum is easier for roofing professionals to shape and lighter in weight. Aluminum must be coated to be preserved. Bare aluminum breaks down when touching alkaline surfaces, such as mortar used to secure bricks. As long as the aluminum is coated, it can be used on concrete or stonework.

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