Roof Flashing Guide: Flashing Types and When to Replace It Skip to content

Roof Flashing Guide: Flashing Types and When to Replace It

roof flashing

A roof flashing is a sheet of metal that’s meant to keep water from getting under your roof and leaking into your home. These are placed on areas in your roof that are prone to water penetration.

All opposing surfaces (roof valleys) should be covered with a roof flashing. If you have a window, vent, pipe, or chimney sticking out of your roof, chances are they have a roof flashing around them.

There are five different types of roof flashing. Let’s look into each of them so you can determine what you have on your roof and know how to deal with them accordingly.

Types of Roof Flashing

Step or Base Flashing

Step or base flashing is used on your chimney walls to prevent water from getting under your roof. It’s often used with other types of flashing and is rarely used alone.

The purpose of a step or base flashing is to make sure that the water flows toward your gutters. It can be placed behind a chimney siding or over bricks and masonry.

Counter Flashing

A counter flashing is usually placed above your roof surface and over a base flashing. It’s the type most often used with a step flashing to waterproof the base of your chimney.

Without either a counter flashing or base flashing, water could easily leak into your home through your chimney.

Continuous or Apron Flashing

A continuous flashing is used where vertical walls intersect the roof. If you have a room above your garage or porch roof, chances are you’ll need this type of flashing for your roof.

It’s also referred to as apron flashing since it pretty much works the same way as an apron. It’s a long piece of metal that directs water down to your roof system.

Valley Flashing

Valley flashing is pretty straightforward—it’s used on the “valleys” of your roof. Wherever there’s an angle change in your roof, there should be a valley flashing to go along with it.

This allows water to have a definite path to flow down to your gutters or off your roof.

Kickout Flashing

As with most houses with gutters, there’s a gap between where the roof ends and where the gutter begins.

A kickout flashing is what bridges the gap between these two. It makes sure that the water goes to the gutter and doesn’t flow to your exterior walls.

Why Roof Flashing Failure Occurs

Now that we know the roof flashing types, it’s time to look into the reasons why a roof flashing failure may occur in your home.

Normal Wear and Tear

Because of weather and temperature changes, roof flashings tend to undergo normal wear and tear (just like your roof and other exterior features in your house).

A roof flashing expands and contracts in response to the temperature, causing them to wrinkle over time. When this happens, water can get into your home and cause leaks.

Settling Foundation

Houses tend to “settle” into the ground they’re built on as time goes by. It’s a normal thing that happens to all new buildings and structures.

But as your house settles, the flashing on your roof may come loose. This is especially true for houses with chimneys. The flashing eventually pulls away from the chimney and causes gaps on your roof where water can get into.

Improper Installation

Some people try to save on roof repairs and end up hiring inexperienced roofers. Some even try to DIY a roof flashing for the same reason.

But then again, improper installation tends to develop into bigger issues for your roof later on. If you’re not sure how to do the job right, hire a professional roofer to do it. Remember that improper installation or a bad roof repair will cost you more in the future.

When to Replace Roof Flashing

No idea how to tell whether it’s time to replace your roof flashing? Don’t worry! Here are some common indicators of a roof flashing that needs replacing as soon as possible.


The weather and other outside elements are usually the cause of rusting on your exteriors. When rust appears, it can cause holes on your flashing and therefore allow water to penetrate through your roof. That’s why it’s important to touch up or replace a roof flashing that already has signs of rust.

Mold or Stains

When a drip edge flashing isn’t properly installed, mold or stains can develop on your house’s fascia boards. It’s more of a cosmetic issue, but when left unaddressed for some time, it could cause bigger problems to your home.


Besides rust, other elements like insects can also cause holes to appear on your roof flashing. Usually, small holes only need to be sealed. But sometimes, with bigger holes, it’s better to replace your whole flashing instead.

Cracks or Dents

Cracks or dents can be caused by strong winds or hail. When this happens, the coating on your roof flashing may be compromised and therefore be prone to other problems such as rusting.

In some cases, pieces of your roof flashing can also go missing. It’s best to replace a missing piece as soon as you notice it to avoid further damage.


A more serious problem happens when leaks appear around your home. Since a roof flashing is meant to keep water out of your home, the presence of a leak usually implies that you could have damage on your roof flashing or on the roof itself.


A roof flashing replacement alone could cost you a lot of money. Roofers also charge you for removing the roofing material on the affected area.

But in a reroofing project, the cost of removing the old roofing material is already factored into the costs, thus allowing you to save some money. It’s also a wiser choice to replace your roof flashing while you replace your roof so that both these features stay durable for a longer period of time.

Roof Installation and Repair

roof flashing replacement

A minor roof flashing replacement or small-scale partial reroofing can be DIY-ed, especially when you have enough background in the field. Check out some guides on shingling your roof or installing a metal roof to see if you can handle the task.

But if you’re not 100% confident that you can take on the job, it’s best to just bring in a roofing professional to make sure the job is done properly. You’ll probably have to spend more money upfront, but at least you can save up on repairs in the future. It’s always an investment worth making.

To recap, here are some things to know about roof flashings:

  • There are five different roof flashing types—base, counter, apron, valley, and kickout flashing.
  • Roof flashing failure can occur by normal wear and tear, a settling house foundation, or improper installation.
  • You’ll know it’s time to replace your roof flashing once you start seeing rust, mold, holes, or dents on it. A more serious problem is when your house starts having leaks.
  • It’s best to have your roof flashing replaced while you’re also taking on a reroofing project. It saves you both time and money.