What Is Roof Flashing & Do You Need Yours Replaced?

Caroline Gilbert
Written by Caroline Gilbert
Updated September 27, 2021
A man in construction gear installing roof flashing
Huntstock / Brand X Pictures via Getty Images

Faulty roof flashing just may be the cause of your water damage

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Without a proper roof flashing system, your entire house is susceptible to some pretty scary stuff. We’re talking about leaks and water damage, mold, rotting, and even pest infestations. 

So, what is roof flashing, and how can you tell if yours needs to be replaced?

Simply put, roof flashing is using a waterproof material (usually steel) to direct water away from the most vulnerable areas of your roof. 

Unless you have adequate roofing experience, we do not recommend messing with your roof flashing as a DIY project. You’ll need to bring in a local roofing professional to help you make repairs to your flashing system. 

However, it’s still useful to know what roof flashing is and how it works. The more you understand what to look for, the sooner you can identify potential issues—ultimately preventing costly, severe damage. 

How Roof Flashing Works

A roof flashing system is designed to direct the flow of water off a roof, bypassing the areas that are the most susceptible to water damage. 

More specifically, roof flashing materials are strategically placed to close corners and crevices where water could seep in without it (think chimneys, skylights, vents, etc.). 

Types of Roof Flashing

A roof with step flashing going up a brick wall
Andrew Gardener - adobe.stock.com

Though the overarching idea of roof flashing is the same, there are different types that fit some situations better than others. Here are seven common types of roof flashing you should know:

1. Base Flashing

Base flashing helps prevent water damage at vertical-to-horizontal intersections on a roof where the roof meets a vertical wall juncture. Base flashing is installed underneath siding and shingles, so it's not easily seen.

2. Step Flashing

Step flashing involves “L” shaped pieces of flashing material that are installed along the corner where the roof meets a sidewall. This type of flashing is partly visible, so homeowners may choose a more expensive material to better match their home’s exterior.

3. Counter Flashing

Counter flashing is placed either above or opposite of base flashing. It’s most commonly used between the roof’s surface and a chimney or a brick wall. It’s purpose is to protect the base flashing.

The most effective way to install counter flashing on a chimney is actually while the chimney itself is being built. However, you can still add counter flashing to an already existing brick structure.

4. Continuous Flashing (aka Apron Flashing)

Continuous or apron flashing is a long piece of flashing that reroutes water from vertical walls and sloped roofs into a gutter.

5. Valley Flashing

Valley flashing involves using flashing materials to line the dip where two sides of a roof come together and form a valley. This helps direct running water off of the roof and into the gutters.

6. Kickout Flashing (aka Diverter Flashing)

Kickout flashing is needed when a gutter ends against a sidewall. This kind of flashing helps prevent water from running down the sidewall and diverts it into the gutters instead.

7. Drip Edge

Drip edge flashing is flashing placed around the edges of a roof to prevent water from dripping behind the gutters and rotting out the roof in the process.

Signs of Flashing Issues

A ceiling and a wall with severe water damage
ReaLiia - adobe.stock.com

Unless you’re an experienced roofing professional, it may be difficult to notice when your flashing system needs to be replaced, but you can look out for these easy-to-spot signs:

  • Noticeable corrosion and rust in flashing and gutters

  • Curling or broken shingles

  • Patches on the roof

  • Water damage in the attic or interior walls (water stains, mold, etc.)

How to Repair Flashing

Roof flashing is a tricky task. Even the smallest spaces that are missed or not properly sealed can be an expensive problem later on down the road. If you think that you may have water damage issues due to faulty flashing, it’s best to hire a local roofing professional for an inspection. 

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