When it comes to protecting your home, your roof’s design and installation matter a lot. But one part people often overlook? Flashing. Metal roof flashing plays a critical role in keeping water out where different parts of your roof connect to walls, chimneys, vents, and skylights. Without proper flashing, even the best roofing system is vulnerable to leaks and water damage.
In this guide, we’ll break down exactly what metal roof flashing is, the different types you might see, and why choosing the right materials makes all the difference.
What is Metal Roof Flashing?
Metal flashing is a thin, waterproof piece of metal that’s installed at vulnerable points on your roof — like where the roof meets walls, around chimneys, or along valleys. Its job is simple but important: direct water safely away from seams and joints so it can’t seep into your home.
Good flashing takes into account the natural expanding and contracting that happens with temperature changes. That means it has to be both strong and flexible.
Flashing can be made from several different roofing materials. Common choices include:
- Galvanized steel: Strong, affordable, and offers great corrosion resistance.
- Aluminum flashing: Lightweight and easy to shape, though it may corrode faster if not properly coated.
- Copper: High-end material with excellent longevity and natural corrosion resistance.
Sometimes roofing cement is used in combination with flashing to create an even tighter seal, especially around tricky areas.
No matter the material, flashing is key for protecting your roof deck and keeping your home dry year after year.
Types of Metal Roof Flashing
There are many types of roof flashing, and each one is designed for a specific spot on your roof. Let’s go through the most common types you’ll find with metal roofing.
Step Flashing
Step flashing is made up of small, overlapping rectangles of metal. It’s used where the side of a roof meets a vertical wall, like around chimneys or dormers.
Each “step” overlaps the one below it, allowing water to cascade safely down and off the roof without sneaking behind the wall. It’s one of the most effective ways to protect against leaks in these tricky transition areas.
Counter Flashing
Counter flashing is installed over the top edge of other types of flashing, like step flashing, to create an extra layer of protection.
It’s often set directly into a brick or stone wall (like around chimneys) to create a watertight seal. By overlapping the underlying flashing, it ensures that water can’t get behind the wall even during heavy rain or strong winds.
Base Flashing
Base flashing is used around vertical structures like chimneys or skylights where two pieces of flashing are necessary to accommodate expanding and contracting.
Because the structure and the roof move at different rates, having two pieces allows for flexibility without compromising the seal. It’s essential for keeping these vulnerable joints dry.
Continuous Flashing
Continuous flashing — sometimes called “apron flashing” — is a long, single piece of metal that runs along where the roof meets a vertical wall.
It’s designed to direct water down the roof away from the seam. However, because it’s one solid piece, it has to be carefully installed to allow for expanding and contracting without cracking or pulling away over time.
Kickout Flashing
Kickout flashing is a small but mighty piece of flashing installed where a roof edge meets a vertical wall.
Its job is to “kick” rainwater away from the wall and into the gutters, preventing it from running down the siding where it could cause rot or mold. Without kickout flashing, hidden moisture damage can build up over the years, leading to expensive repairs.
Valley Flashing
Valley flashing is placed in the valleys formed where two roof slopes meet. Valleys collect a lot of water, so this is a critical area to protect.
A strong, properly installed piece of valley flashing helps guide water safely down the valley and off the roof without it seeping into the structure.
Vent Pipe Flashing
Any pipe sticking up through your roof — like a plumbing vent — needs vent pipe flashing. This flashing usually looks like a cone-shaped piece of metal or rubber that fits snugly around the pipe.
It prevents water from sneaking down the sides of the pipe and into your attic or walls. Flashing around pipes must stay flexible to accommodate movement from wind, heat, and settling.
Skylight Flashing
Skylight flashing is specifically designed for skylight windows. Since skylights create big openings in the roof, they need special care to avoid leaks.
Most skylight manufacturers provide custom flashing kits that work perfectly with their windows, including a combination of step flashing, continuous flashing, and sometimes roofing cement for an extra layer of security.
Best Materials for Metal Roof Flashing
Choosing the right material for your metal roof flashing matters just as much as the type. Here’s a quick look at the best options:
Galvanized Steel
Galvanized steel is one of the most common choices because it’s affordable, strong, and has excellent corrosion resistance thanks to its zinc coating. It’s a great match for most metal roofing systems.
Aluminum Flashing
Aluminum flashing is lightweight and easy to work with. It’s a good choice for complicated roof layouts or areas where flexibility is needed. However, unless it’s coated, aluminum can corrode faster than steel, especially near salty coastal air.
Copper
Copper is expensive but incredibly durable. It naturally resists corrosion without any additional coatings. Over time, it develops a beautiful greenish patina that many homeowners love.
When choosing flashing, it’s important to match your flashing material to your roofing materials to avoid galvanic corrosion. For example, don’t mix copper flashing with a galvanized steel roof unless proper barriers are used.
FAQs About Metal Roof Flashing
What is the purpose of metal roof flashing?
Metal roof flashing directs water away from vulnerable areas on your roof, like where two surfaces meet or where something sticks through the roof (like a vent or chimney). It helps prevent leaks and protects your home’s structure.
Can you use aluminum flashing with metal roofs?
Yes, you can use aluminum flashing with metal roofs, but it’s important to ensure it’s coated or protected to prevent corrosion. Also, make sure it’s compatible with your specific metal roofing to avoid galvanic reactions.
How long does galvanized steel flashing last?
When properly installed and maintained, galvanized steel flashing can last 20 to 30 years or longer. Its corrosion resistance makes it a durable choice for most climates.
Does metal roof flashing require roofing cement?
In some areas, especially around chimneys or complex penetrations, roofing cement may be used alongside flashing for an extra seal. However, flashing should do most of the work without relying on cement.
What’s the most important flashing to install on a metal roof?
It’s hard to pick just one! Valley flashing, step flashing, and vent pipe flashing are some of the most critical, but every type plays an important role in preventing leaks and extending the life of your roof.
Protect Your Home with Professional Metal Roof Flashing Installation
Installing metal roof flashing isn’t just about slapping down some metal and hoping for the best. It requires skill, attention to detail, and the right materials to make sure your roof stays leak-free for decades.
Ready to make sure your metal roof is protected for the long haul? Contact Mountaintop Metal Roofing today for a free quote. Our expert team knows how to install flashing the right way — so you can enjoy peace of mind, rain or shine!