What is Roof Flashing?

Roof flashing provides protection for different areas of your roof and works in conjunction with your roofing material. Flashing is applied to roofing corners and valleys, as well as objects that jut out through your roof. So let’s talk about what exactly is roof flashing. How does it work? Where is it used? And the different roof flashing types such as counter flashing or step flashing.

Flashing is usually built out of metal, but it may contain steel, zinc, copper, aluminum, and even plastic or rubber. Flashing is used to keep roof components waterproof and prevent any damage. Without flashing, roof components such as the junctions between walls, dormers, or chimneys may come into contact with water which can saturate, leak, and damage the component or the structure of the house. In short, the roof flashing keeps the integrity of your home intact.

The way that flashing works is by connecting to various roofing components, and it can be overlapped and connected with one another in order to keep leaks from penetrating the roof or any of the structures on your roof. Flashing can be installed with nails, glue, and caulking in order to keep your roof waterproof.

Roof flashing installation occurs throughout your roof, including all of the following places:

• Valleys and Joints – the joints found throughout your roof structure are more susceptible to penetration from water, as are roof valleys. Roof joints often aren’t watertight, and roof valleys collect more water than the rest of the roof. The roof flashing ensures that these critical areas of your roof are protected. 

• Roof Protrusions – If there’s anything jutting out of your roof, there should be flashing to protect it. If, for instance, you have cables that tie into a satellite that’s installed on your roof, flashing can protect the opening for the satellite cables free from water and prevent any future damage. 

• Drip Edging – Drip edging is flashing that is applied to the edges of roofs where there aren’t gutters. Think of drip edging as a specialized roof flashing at the edge of your roof that acts as guides to prevent water from getting behind gutters and ensure that all water is directed away from your roof. 

• Chimneys – Chimney flashing is necessary since water can run through and collect right at the base of a chimney. Chimney flashing should be installed at the base of your chimney to keep water from infiltrating the joint between your roof and your chimney. 

• Pipes – It’s likely that your roof has a few pipes that penetrate the surface of your home. For instance, you probably have drain-waste vents which keeps the pressure from building up in your plumbing. These pipes can compromise a waterproof roof if they are left unprotected. Specialized “pipe boots”, which work exactly as it sounds, can be placed around these pipes in order to protect your roof. 

• Kickouts – Kickout flashing is installed at the lowermost joint between your roof and your wall. The kickout flashing, also known as diverter flashing, diverts rainwater away from your wall and into your gutter to avoid any kind of saturation leaks in your roof.

If you have ever noticed that there are any leaks coming from around your chimney or vent, most likely your flashing was not installed correctly or is no longer sufficient. The main purpose of roof flashing is to protect your home from moisture & saturation. The flashing extends below your roofing and adjacent to siding to create a solid, weatherproofing seal on your home to protect you from the elements. It is also much more durable and lasts longer than trying to seal or caulk around the spaces. Before sheet products were available, builders had to use different methods to try to minimize water penetrations. These methods included angling roof shingles away from the joints, installing chimneys at the ridge, and building steps off to the sides of chimneys to divert water.

Furthermore, roof flashing is less susceptible to temperature variations. If and when the other components of your roof shift slightly, due to expansion from heat or ice, the flashing will still be able to act as a barrier from the elements. If you have any concerns or thoughts that you could be having leaks call your local roofing contractor.

Flashing also adds a clean, finished look to your roof. There are areas of roofs and exterior walls that are more susceptible to leaks and water damage such as the valleys or junctions where roof sections or walls meet. It is usually installed around structures that intersect with the roofline such as dormers, skylights, vents, and chimneys. Flashing comes in a variety of materials to accommodate the desired look for the consumer. Although you may see rubber or plastic flashing out in the market, metal flashing is the more prominent kind of flashing. One of the most common types of metal flashing material used is aluminum because it is usually the most cost-effective, durable, and weather-resistant.

Counter Flashing

For starters, counter flashing is only one type of flashing and is a technique that is used to help prevent moisture from penetrating into a home behind the vertical flange of a headwall or sidewall flashing. Pieces of metal are installed in order to prevent water from passing through a structure at its joint and ensure the water is directed away from the structure. Sometimes the material used, such as vinyl, for the exterior wall siding will be enough to serve as counter flashing itself and other times a separate element is installed. This is especially important in a structure where walls are either brick or stone. The counter flashing installation process is one of the most important parts of completing any roofing system. This type of flashing should be used in conjunction with base and step flashing, to help form a waterproof barrier.

The waterproof membrane is the first layer that is laid down before the shingles are installed, called the base flashing. This membrane not only covers the first layer of the roof but also gets turned up the nearby walls or chimneys to help with the flashing process of any joints or valleys between structures. Next, L-shaped pieces of metal, typically aluminum, are placed under each shingle that is installed next to a vertical wall. One side of the L-shaped aluminum flashing lays underneath the shingle while the other side attaches up against the side of the wall. This layer is called the step flashing.

In contrast to step flashing, the next layer is installed as a continuous strip. It is installed either behind or on top of the wall adjacent to the shingles and covers the step flashing. This final layer is called counter, cover or cap flashing and most commonly consists of aluminum or galvanized steel, but is also seen made with copper, tin or even plastic. Depending on the situation, a roof with step flashing installed could sufficient in itself when combined with vinyl siding that can double as counter flashing as long as the step flashing goes underneath it. Otherwise, counter flashing is a critical requirement for all roofs.

Counter Flashing Installation Methods

Counter flashing installation can be done using one of three techniques. The first is through-wall counter flashing, which secures the flashing material to the wall cavity and the exterior siding or masonry covers it. This type of installation is only plausible during a new construction project; otherwise, it typically proves to be cost-prohibitive.

The second technique used to install counter flashing is called surface-mount flashing. This technique attaches the flashing to the exterior siding by using a sealant, typically caulk, to seal the top of the surface-mount flashing. It’s the least expensive method of installation, however, the caulk seal will need to be monitored and eventually repaired or replaced over time because it will inevitably break down.

Reglet flashing is the compromise between through-wall and surface-mount flashing. A cut is made into the exterior masonry at a 90-degree angle and the flashing material is secured in the groove made by the 90-degree cut and bent down to run parallel the exterior masonry. Although it is a more expensive and invasive technique than the surface-mount flashing, reglet flashing does not need maintenance and will last much longer than a sealant. Because of this, reglet flashing is a more convenient, long-lasting option and is recommended over the surface-mounted flashing.

Counter Flashing at Brick Headwalls and Sidewalls

Installing headwall and sidewall flashing correctly becomes more time consuming when the exterior wall covering is brick or stone.“Time-consuming” can mean “more expensive”, which is why a lot of the counter flashing you’ll see at brick and stone walls will be incorrectly installed and will solely rely on some sort of sealant to prevent moisture intrusion. Sealant eventually dries, shrinks and cracks, leaving room for moisture intrusion and future water damage. This is why it is recommended to install regret flashing to ensure the most protection from moisture intrusion.

Step Flashing

Step flashing is an L-shaped piece of metal, typically aluminum or galvanized steel, and is used where a sloped roof intersects a vertical wall. Step flashing is interwoven with the shingles and act essentially as shingles with an unturned leg to allow a transition of the vertical drainage plane of the wall to the drainage plane of the roof. One side of the L-shaped step flashing is behind the vertical drainage plane or sealed to it with some sort of sealant and/or sheathing tape. The bottom leg of the step flashing is placed over the roof drainage plane. A critical component of the step flashing is the piece that is at the end of the slope of the roof is called the kickout flashing. This roof flashing directs water away from the adjoining wall and ensures that the step flashing is not collecting water on the surface of that wall.

Is Continuous Flashing Better Than Step Flashing?

Continuous flashing is sometimes seen where a roof meets a sidewall instead of step flashing, but in the long run, step flashing will do a better job of preventing water leaks. 

Step flashing redirects the water back onto the shingle and away from valleys and joints. Even if one piece of step flashing fails, the next flashing and shingle below it start the process over again, providing a system to protect your roof from water damage. Continuous flashing against a sidewall is one way to install flashing on a roof, but it’s not the correct way. Some may think that a single piece of flashing would offer more protection than many pieces of step flashing, but it doesn’t work that way. Once even a small section of the continuous flashing fails, you’ll have a leak. Each additional rainstorm will add more water, and before you know it, you’ve got rotted wood and a roof inspector in your home.

Step flashing offers far better protection from leaks because even if a single piece of step flashing fails, the water just hits the next step of the flashing. The flashing then directs the water onto the shingle and the water drains down the roof.

Kickout Flashing

Kickout flashing which can also be called diverter flashing is a special type of flashing installed at the edge of the flashing that diverts rainwater away from the cladding and into the gutter. When your roofing contractor installs kickout flashing properly, the flashing will provide excellent protection against the penetration of water behind the exterior wall covering where the flashing ends. Kickout flashing is required regardless of the roofing material excluding brick or concrete block.

Yes, there can be several factors that can lead to rainwater intrusion, but a missing kickout flashing, in particular, often results in concentrated areas of water accumulation and potentially severe damage to exterior walls. If you happen to find saturation and possibly plant growth on the exterior siding of your home, you may have missing kickout flashing causing the water damage.

Apron Flashing

Apron flashing is the metal that covers the transition between a roof slope and a roof penetration such as a dormer or chimney. Having this flashing properly installed is crucial in protecting some of the most vulnerable areas of your roofing system.

Apron flashing is usually applied as part of the two-piece roofing system. The apron is the lower L shaped piece that replaces the normal step flashing, which covers the roofing material and extends up the vertical surface of the roof penetration. The second part of the system is something we’ve touched one, which is the counter flashing that extends parallel from the vertical surface and covers the vertical leg of the apron flashing.

The Importance

Now that you have had a breakdown of the important role that roof flashing plays when it comes to the protection of your roof, it is easy to see why it is needed on almost all roofing projects. Without roof flashing, our roofs would be much more susceptible to water damage, costing homeowners thousands of dollars in repair or replacement. So when having your next roof inspected or installed, be sure that your flashing is properly installed by your local roofing contractor to ensure the best protection for your roof.