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The Secret Life of Roof Flashing

Updated: May 19, 2023

Roof Flashing

Everything You Need to Know About Roof Flashing in One Simple Guide


Roof flashing is the unsung hero of the roofing world. If your roof were a football team, the flashing at the roof would be like the offensive line. Your shingles get all of the attention and act like the face of the roof, much like the team’s quarterback. The king post, strut, and rafters are like the fullback that gets all the attention for being tough. Like the offensive line, a flashing roof does the work behind the scenes. Without the proper roof flashing, the entire team is at risk, and the roof could fail.


Since this unsung hero doesn’t get much attention, it’s easy to forget it’s there. It’s important to know what roof flashing is, how it works, and when it needs to be repaired or replaced. Otherwise, your roof could experience some pretty scary stuff.


Read on to learn everything you need about roof flashing in this guide.


What is Roof Flashing?

To understand roof flashing, you should first look at the various parts of a roof. To the naked eye, a roof appears to just be a large cover on top of your house. We expect a roof to protect the house from various weather conditions, keep critters out of our attics, and give the house a finished look. A roof is actually made up of several layers, each one playing a critical role.


A Quick Look at Your Roof

While different roof types have varying parts, some basic layers make up most modern roofs.


  • Truss: the framework of the roof. The truss is made up of various parts that support the roof.

  • Covering: what is nailed to the rafters to stop the rain, sun, wind, snow, etc. from entering the structure. Coverings are often made from iron sheets, tiles, concrete, slate, etc.

  • Rafters: these run from one end of the roof to the other to form the roof's framework.

  • Ridge: the highest point of the roof.

  • Eaves: the lowest point of a pitched roof.

  • Sheathing: OSB, plywood, or particleboard placed over the rafters to provide strength and support.

  • Underlayment: waterproof material placed over the sheathing to protect the roof from water.


Other roof parts play essential roles, but we should understand how complex a roof is. You may wonder, “ok, great, but what is flashing on a roof?” That’s a great question!


Roof Flashing Basics

Roofs are made to help rainwater run off the roof, which is why most modern roofs are angled. There are, however, vertical features that protrude through the roof, such as heat vents, chimneys, parapet walls, dormers, skylights, and more. These areas create flat pockets where water can build up, seep into the roof, and, unchecked, can cause massive damage to the house.


To prevent the potential damage from pooling water around these vertical structures, professional roofers install roof flashing. This flashing is typically a thin metal made from rust-resistant materials like G-90 galvanized steel, copper, or aluminum. Some companies even use lead or zinc alloy, but these aren’t as common.

 Flashing is used to close the joints between the roof and other roof features, like chimneys and vents, to keep water from causing problems like wood rot, shingle damage, erosion, leaking, or deck collapse.

Installation 101

Due to the complexity and importance of this roof element, installing flashing on a roof is not meant for do-it-yourselfers. Professional roofers have two options when installing roof flashing. The first is nailing the flashing into the roof.


While nailing is typically faster, it does pose some risk. If the flashing is nailed to both the roof and the vertical protrusion, the pressure caused by shifting wood can cause the flashing to deform. To combat this problem, roofers will typically only nail the flashing to one of the surfaces.


The other option is to use the appropriate roofing cement. This cement shears to both surfaces to create a waterproof seal between the roof and the flashing. The adhesive can also flex and move with the house as it shifts over time. You also don’t add any unnecessary holes in the roof structure that come from nails. Roofing cement can add a little time and cost to the overall roofing project.


Since flashing comes in various shapes and sizes and is used in different areas of the roof, not every type of roof flashing is installed the same way. Unlike sealant or tar, flashing, when properly installed, is made for long-term use and protects the roof for the long haul.


The Many Faces of Roof Flashing

While the basic idea of roof flashing is the same across brands, styles, and capabilities, there are a host of types that are perfect for different situations. There are seven primary kinds with which you should be familiar:


Base Flashing

Base flashing is used at the base of vertical-to-horizontal intersections where the roof meets a vertical well. This kind of flashing is installed underneath siding and shingles and is virtually impossible to see.


Step Flashing

Step flashing is used where the roof meets a sidewall and uses an “L” shape to do its job. Since step flashing is often partially visible, homeowners might choose a better-looking and more expensive material to match their home’s style.


Counter Flashing

Counter flashing is used above or opposite base flashing, which helps protect the base flashing. Counter flashing is often called chimney flashing because it is most effectively installed when the chimney is being built. Both wood and metal roof chimney flashing can be installed or repaired to an existing brick structure, but it requires the work of a pro.


Continuous Flashing/Apron Flashing

Apron flashing is most commonly used with your roof’s gutter system. It is most often a long piece of roof flashing that reroutes water from vertical walls and sloped roofs into your gutter system.


Valley Flashing

A roof’s valley is used when two sides of a roof come together to form a valley. Flashing is used to line this valley to help direct water off of the roof and into your gutters.


Kickout Flashing/Diverter Flashing

There are times when a gutter ends against a sidewall. Kickout flashing is used to prevent water from running down the sidewall. Instead, diverter flashing diverts the water back into the gutters.


Drip Edge Flashing

Drip edge flashing is used around your floor’s edges to prevent water from dripping behind the gutters and damaging the roof.


Skylight Flashing

While most skylights come with flashing, you could end up with units that do not. A roofing contractor can buy or create something to protect the seams around this window.

Pipe Jack Roof

Pipe Jacks aren’t necessarily the same as other kinds of roof flashing, although they provide the same service. A pipe jack is a pre-formed flange placed over a vent pipe to seal the roof around the pipe’s opening. They are sometimes called pipe boots, jack plumbing, or no-caulk leads. Every roof has pipes that penetrate the roof, from HVAC vents to plumbing vents. Pipe jacks help protect those penetrations from taking in water.


How To Tell When Your Roof Flashing Has Issues

Since roof flashing is at least partially, if not entirely, hidden, it is not always easy to see when flashing pieces need to be replaced. An experienced roofing company knows precisely what to look for and can give you an accurate idea of your roof’s condition, including the flashing.


There are, however, several signs that are easy to spot. It’s crucial that you look at your roof every now and again to catch issues that turn into real problems. Here’s what you can keep an eye on:


  • Curling or broken shingles

  • Patches on the roof

  • Noticeable corrosion and/or rust in visible flashing and gutters

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

Call a local roofing company immediately if you notice any of these signs. It will take an experienced professional getting up on the roof and inspecting the issues to know the extent of the damage.


Flashing Repair: Leave It to the Pros

Roof flashing isn’t as easy to repair or replace as you might think. Finding the full extent of the damage may require removing shingles and inspecting seams in the roof, vent protrusions, and more, and these areas may require additional repairs before new flashing can be installed.


More importantly, flashing plays such a crucial role in protecting your roof that you can’t afford to make a mistake. Even a tiny area that isn’t installed correctly can lead to significant damage down the road.


Luckily, if you are in the Lafayette, LA, area, Hibbard Roofing and Construction is here for you. Are you worried about water damage from faulty flashing? Did a recent storm pass through and cause concerns for your roof? Is your insurance company giving you the runaround? Give us a call or contact us online to schedule your free roof inspection and repair estimate right away. When it comes to your roof flashing, you can’t afford to be blindsided. Give Hibbard Roofing and Construction a call today.



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