What Is Step Flashing (and What You Might Want to Know About It)

When you look at your roof, you probably notice the shingles first. But the true secret to a long-lasting, leak-free roof lies in the details you might not see, specifically, the seams where your roof meets a vertical surface like a wall or chimney.

These intersections are the most common entry points for water, and protecting them requires a specialized component. This is where step flashing comes into play.

Understanding the role of flashing is the first step toward preventing some of the most common and costly roof leaks. It’s the series of metal pieces expertly installed to channel water safely off your roof. While there are several types, each with a specific job, they all work together to keep your home dry.

Before we dive deep into step flashing, here’s a quick overview of the main types of flashing you might find on your roof:

• Step Flashing: Individual L-shaped pieces of metal layered with shingles along walls and chimneys.
• Counter Flashing: A second layer of flashing that covers the top of the step flashing, sealing it from above.
• Apron Flashing: A single piece of metal used where the low end of a sloped roof meets a wall or the front of a chimney.
• Valley Flashing: A metal channel installed in the ‘V’ shaped area where two roof planes join.

Now, let’s get into the step flashing details.

What Is Step Flashing?

Step flashing is a system of individual L-shaped metal pieces designed to protect the joints where a sloped roof meets a vertical surface, like a wall or chimney.

Unlike other types of flashing that come in long, continuous pieces, step flashing is installed in overlapping sections, almost like shingles, to create a watertight barrier that directs water safely off the roof.

When you look at step flashing on a roof, it differs from other flashing types mainly in its shape and placement. While valley flashing runs along roof valleys to guide water down, and apron flashing sits at the base of dormers or chimneys, step flashing is installed piece by piece up the side of a wall or chimney. Each “step” overlaps the shingle below it, allowing rainwater to cascade down without slipping behind the siding or wall. This overlapping pattern is what gives it both its name and its effectiveness.

What Is Step Flashing Used For?

The main purpose of step flashing is leak prevention in spots where the roof meets another structure. These transition points are among the most common sources of water intrusion in Atlanta homes, especially during heavy rain or wind-driven storms. Step flashing is typically used in three critical areas:

1. Vertical walls: Where the edge of the roof meets siding, step flashing prevents water from seeping behind the wall surface.
2. Chimneys: Along the sides of a chimney, chimney step flashing keeps water from pooling at the base or sneaking through small gaps in the masonry.
3. Dormers: These small roof extensions need extra protection where their sides meet the main roof slope.

When properly installed, step flashing works hand in hand with counter flashing (which covers it) to provide a two-layer defense against leaks.

Where Step Flashing Is Used in Roofing

You’ll typically find step flashing roof installations in these key areas:

Each of these locations is exposed to constant runoff, so missing or damaged flashing in any of them can lead to water damage, wood rot, or mold growth over time.

Step Flashing Details

For step flashing to do its job correctly, the details of the installation matter immensely, and here’s why:

• Dimensions & Materials: Pieces are typically bent from aluminum or galvanized steel, though copper step flashing is used for copper or slate roofs for its durability and aesthetic. A common size is around 5 inches by 7 inches, but the exact dimensions can vary depending on your roof’s slope and the type of shingles used.
• Overlap Requirements: Each new piece of flashing must overlap the one installed below it by at least two inches. This creates a cascade effect, ensuring that any water that gets onto the flashing is directed on top of the next piece, and so on, until it’s safely away from the wall.
• Integration with Shingles: A roofer lays a course of shingles, installs a piece of step flashing over it against the wall, and then lays the next course of shingles over that piece of flashing. You should only see a small portion of each piece of flashing peeking out from under the shingle above it. According to inspection standards from organizations like InterNACHI, this proper layering is non-negotiable for a professional step flashing roofing job.

Step Flashing Materials & Options

Just like you have choices for your shingles, you also have options when it comes to the material for your step flashing. The right choice depends on your budget, the type of roof you have, and the aesthetic you’re aiming for. Each material offers a different balance of durability, cost, and appearance.

1. Aluminum Step Flashing

Let’s start with the most common player on the field: aluminum step flashing. This is the go-to choice for the majority of residential roofing projects in the Atlanta area, and for good reason. It’s lightweight, easy for professional roofers to cut and bend on-site, and very cost-effective.

However, it has its downsides. Aluminum is a softer metal and can be prone to corrosion over time, especially if it comes into contact with certain materials like mortar from a chimney or treated wood. This chemical reaction, known as galvanic corrosion, can slowly eat away at the metal, potentially leading to failures down the road.

2. Copper Step Flashing

For homeowners looking for unparalleled durability and a touch of classic elegance, copper step flashing is the premium choice. It is incredibly resistant to corrosion and can easily last for 50 years or more, often outliving the shingles around it.

Over time, copper develops a beautiful blue-green patina that is highly sought after, especially for historic or high-end homes in neighborhoods like those in Roswell or Canton. While the upfront investment is higher, its longevity makes it a worthwhile consideration for a “forever” roof.

3. Colored Step Flashing

Want your flashing to blend in seamlessly with your roof? Many homeowners prefer colored step flashing, which is typically aluminum or steel that has been painted. This allows you to match the metal pieces to your shingle or trim color, creating a more cohesive and less noticeable finish.

The factory-applied paint provides an extra layer of protection, though it can fade or chip over many years of exposure to the elements.

4. Metal Step Flashing

While aluminum and copper are specific types, you’ll often hear the general term “metal step flashing.” This usually refers to either aluminum or another common option: galvanized steel. Steel flashing is coated with a layer of zinc to prevent rust. It’s a bit stronger than aluminum and is also a very durable, cost-effective choice for your roof step flashing.

5. A Note on “Shingle Step Flashing”

This is an important point for homeowners to understand. You may hear about using shingles or tar as a form of flashing. This is not a professional or acceptable practice. Proper step flashing roofing requires interlocking pieces of metal.

Using roofing cement or cutting shingles to mimic the shape of flashing is a shortcut taken by inexperienced or dishonest roofers. This method will crack, dry out, and fail quickly, leaving your home vulnerable to serious water damage. If a contractor suggests this, it’s a major red flag.

Step Flashing on Chimneys

Chimneys are one of the most leak-prone areas on any roof. The joint where brick or stone meets the shingles naturally collects water, and without proper flashing, that moisture can find its way inside your home.

This is where step flashing on chimneys plays a critical role. It forms the first line of defense, redirecting water away from the chimney base and roof intersection before it can seep into the masonry or decking below.

Step Flashing Chimney vs. Chimney Step Flashing

You may see both “step flashing chimney” and “chimney step flashing” used interchangeably, and in practice, they refer to the same concept. Step flashing for chimneys consists of a series of small, L-shaped metal pieces installed along the sides of the chimney where it meets the roof. Each piece overlaps the next, creating a “stepped” pattern that channels water downward and away.

This approach differs from continuous flashing systems, which use one long metal strip. The step-by-step layering makes chimney flashing more adaptable to uneven surfaces and ensures water can’t sneak behind the metal.

Integration With Counter Flashing vs. Step Flashing

Proper chimney waterproofing actually involves two layers of flashing: step flashing and counter flashing. These work together but serve different purposes.

• Step flashing is installed first, tucked under the shingles and alongside the chimney base. It catches and redirects runoff from the roof.
• Counter flashing is then installed over the top edge of the step flashing, embedded into the mortar joints of the chimney. It seals and protects the upper edge of the step flashing from exposure to rain, snow, or debris.

This combination creates a durable, watertight system. If only one of the two is used, or if they’re improperly overlapped, leaks can quickly develop around the chimney.

Step Flashing vs. Counter Flashing Roles

Proper chimney waterproofing actually involves two layers of flashing: step flashing and counter flashing. These work together but serve different purposes.

1. Step Flashing’s Role: As we’ve discussed, these pieces are woven in with the shingles. The bottom of the “L” shape sits under the shingle above it, and the vertical part runs up the side of the chimney brick. Its primary job is to catch water flowing down the roof and keep it on top of the shingles, preventing it from ever touching the roof deck.
2. Counter Flashing’s Role: This is the cap that seals the system. Counter flashing is a separate piece of metal that is embedded directly into a mortar joint of the chimney. It then folds down and lies over the top of the vertical part of the step flashing. Its only job is to stop water from running down the face of the chimney and getting behind the step flashing.

Think of it this way: step flashing protects the roof deck, and counter flashing protects the step flashing. Together, they create a complete seal. This two-part system is a non-negotiable standard for professional roofing and is emphasized by organizations like the Chimney Safety Institute of America (CSIA).

When To Choose Copper Step Flashing For Chimneys

For homeowners in upscale areas like Roswell or historic districts in Atlanta, copper step flashing is often the top choice. The reason is that copper is one of the most durable flashing materials available. Copper resists corrosion, stands up to decades of harsh weather, and can last as long as the chimney itself with minimal maintenance.

In high-end or historic homes, copper step flashing and counter flashing together create a premium, polished appearance that blends naturally with traditional architecture. Over time, the copper develops a soft patina that enhances the home’s character while continuing to protect against leaks.

Common Problems with Step Flashing in Georgia

While proper step flashing is your roof’s best defense against leaks at walls and chimneys, it’s also one of the most common areas where roofing jobs go wrong.

Here in Georgia, with our heavy rains and high humidity, any small installation error can quickly turn into a significant problem. Many of the leaks we repair are directly tied to flashing that was installed improperly from the start.

Before we break down the details, here’s a quick look at the most frequent issues we see.

Poor Installation

This is, by far, the number one cause of flashing failure. A correct step flashing installation is a meticulous, step-by-step process. Unfortunately, inexperienced or rushed roofers often take shortcuts that compromise the entire system.

One major red flag is seeing nails driven through the face of the flashing. Each piece of step flashing on a roof should only be secured with one nail at its top corner, which is then covered by the next shingle and the wall siding. Nails anywhere else create a hole for water to enter.

Another critical error is using one long piece of metal (called “L-flashing”) instead of individual “steps.” This single piece can’t expand and contract with temperature changes, causing it to warp and pull away from the wall, breaking the seal.

Rusting/Corrosion

Even properly installed flashing can fail if the wrong material is used. The humid Georgia climate is tough on metal. Lower-grade galvanized steel can rust over the years, while standard aluminum step flashing can corrode when it comes into contact with the alkaline chemicals in brick mortar.

Once rust or corrosion starts, it creates tiny pinholes in the metal. While they may be invisible from the ground, they are large enough to allow water to seep through during a heavy downpour, leading to slow leaks that can cause significant damage to your roof deck and attic before you even notice them.

Missing Kickouts

This is a small detail with huge consequences. A “kickout flashing” is a specially formed piece of metal installed at the very bottom of a roof-to-wall line, right where the water is supposed to exit into a gutter. Its job is to “kick” the water out and away from the wall.

Without a kickout, water can continue running down the wall, getting behind your siding. This is a recipe for disaster. The trapped moisture leads to wood rot, mold growth, and can even attract termites. According to building science experts, managing water at these intersections is critical for wall durability. A missing kickout is a sign of an incomplete job and can lead to thousands of dollars in siding and structural repairs, all because one small, critical piece of flashing was left out.

Cost, Sizes, and Purchasing

When you’re facing a roof repair or replacement, it’s natural to wonder about the cost of the components involved. While you might see step flashing on the shelves of a local hardware store, it’s important to understand that the price of the material is just a tiny fraction of its overall value. The real investment is in the expertise required to install it correctly.

Step Flashing Bundle Pricing

For the most part, standard aluminum step flashing is not an expensive material. It’s typically sold in bundles, and what a homeowner might expect to pay can vary.

• A bundle of 25 or 50 pre-bent aluminum pieces can range from $20 to $50, depending on the thickness (gauge) and size.
• Copper step flashing is a different story. It’s sold by the piece or in much smaller quantities and is significantly more expensive. The price fluctuates with the commodities market, but expect it to be several times the cost of aluminum.

Step Flashing Sizes

There isn’t one universal size, but there are common industry standards that work for most residential asphalt shingle roofs. A typical piece of step flashing might be 5 inches by 7 inches, 4 inches by 4 inches by 8 inches, or a similar dimension.

The goal is to have enough metal to extend at least 4 inches up the vertical wall and 4 inches out onto the roof deck, ensuring it’s properly covered by the shingle. The correct size also depends on the pitch of your roof; steeper roofs may require larger pieces.

Local Suppliers

For homeowners looking to do a small DIY repair (which we strongly advise against for flashing), you can find basic materials locally. You’ll see step flashing at Home Depot, Lowe’s, or other big-box hardware stores in the Atlanta area.

However, professional roofing contractors typically source their materials from dedicated roofing supply houses. These suppliers offer a wider range of gauges, colors, and higher-quality metals that aren’t always available to the general public, ensuring a more durable and professional finish.

Step Flashing Calculator for Material Estimating

If you’re curious about the quantity needed, the math is fairly simple for a straight wall. You generally need one piece of flashing for every course of shingles. For example, if your shingles have a 5-inch exposure (the part you see), you’ll need one piece of flashing for every 5 inches you go up the roof.

While you might find an online step flashing calculator, remember it’s only for a rough material estimate. It cannot account for the custom cuts needed for corners, the integration with a chimney’s counter-flashing, or the critical final kickout piece.

Why Professional Installation Avoids Costly Mistakes

Here’s the bottom line: the material cost for flashing is minimal. The real cost comes from the damage that occurs when it’s installed incorrectly. That $30 bundle of aluminum step flashing, if nailed in the wrong place or not layered properly, can easily lead to thousands of dollars in water damage, structural rot, and mold remediation.

Hiring a professional roofer for a step flashing installation isn’t just paying for materials and labor; it’s investing in peace of mind. You’re paying for the experience to know exactly how to integrate the flashing with your specific roof type, how to handle tricky angles, and how to ensure the system is completely watertight for years to come. It’s the difference between a quick patch and a permanent solution.

Conclusion

Step flashing might not be the most visible part of your roof, but it’s one of the most important. It works quietly in the background, protecting your home from leaks where the roof meets walls, dormers, or chimneys. When it’s properly installed and maintained, step flashing prevents costly water damage, mold growth, and structural issues, especially in Georgia’s humid, storm-prone climate.

Whether you’re dealing with a small leak near your chimney or planning a full roof replacement, having the right materials and professional installation makes all the difference. From aluminum step flashing to copper step flashing for historic homes, the right solution depends on your home’s design and budget, but the one thing you shouldn’t compromise on is quality workmanship.

If you suspect a problem with your roof flashing or simply want peace of mind before the next heavy rain, contact Mr. Roofer today.

Our experienced Atlanta roofing team specializes in step flashing installation and roof leak repair, ensuring your home stays dry, durable, and beautiful for years to come.