Flashing Best Practices
Roll, Step And Roof-To-Wall InstallationPaul Casseri, Product Manager
Flashing plays a critical role in shielding a roof from water damage. Essential for leak-proof performance, flashing protects intersections of the roof plane and penetrations through the roof surface.
Installation methods and materials can vary based on region and weather. For example, some roofers may use aluminum instead of steel or copper. And some may use caulk on nail holes while others use tar.
The most important rule of any roof installation is to follow ARMA guidelines.
Atlas Roofing partnered with professional contractor Mic Barringer, owner of Barringer Brothers Roofing in O’Fallon, IL, and asked him to share some of his best practices for flashing installation.
Installed along headwalls, roll flashing prevents water from penetrating a roof deck.
Roll flashing comes in a variety of metals, including steel and copper. These durable materials are typically used in Northern states, where roofs are prone to ice dams, and the Southeast, where roofs must withstand high winds and wind-blown rain.
Where Barringer lives in Illinois, the weather doesn’t get worse than an occasional downpour, so he uses aluminum roll flashing.
“Where we are, we get down-directional rain — we don’t get storms here,” he explains. “We even tape our flashing, and people will criticize if it’s not the way they do it — everybody does it differently. But here, this is 100% standard.”
How To Install:
- Pull out the length of roll flashing needed for the headwall and extend it at least 4 inches past the sidewall.
Tip: Pull roll flashing from the center so it doesn’t uncoil and can easily be reused.
- Adjust roll flashing so the center of the metal meets the bottom of the headwall, then nail it to the roof.
Tip: Push a hammer into the roll flashing as far as you can and slide it across the metal to create a 90-degree angle.
- If necessary, nail roll flashing to the headwall to help smooth out wrinkles.
Note: Barringer acknowledges that nailing is not a preferred practice, but it gets the length of roll flashing as flush to the headwall as possible. To keep water from shedding behind flashing, he uses Zip System Tape, although he points out that others may use Tyvek. Starting the overlap from the bottom up, he adheres flashing to the oriented strand board (OSB).
- Cut the extended section of roll flashing straight down, even with the sidewall and nail it to the roof deck, giving step flashing an area to drain off.
Tip: This method takes the place of pre-bents, which can be difficult to fit to the corner. If you end up with a pinhole, simply cover it up later with caulk.
The small “steps” created by step flashing allow water to flow down the sidewall of a roof.
Like roll flashing, step flashing also comes in a variety of metals, with aluminum and copper being the most commonly used.
Barringer uses pre-milled aluminum step flashing because it already has a perfect 90-degree angle bent into it. And because each shingle is going to drain off, he installs one piece of step flashing per shingle, based on ARMA guidelines.
In states such as Minnesota, Florida and the Carolinas, roofers typically use steel or copper step flashing and bend it themselves and may also solder pieces together to protect a roof from ice dams and rain, Barringer says.
Ice and water underlayment is commonly installed behind step flashing in states with heavy storms and snow. In O’Fallon, Barringer says they use ice and water on eaves and valleys, but they’re not required to use it on protrusions because they don’t get the type of weather that would warrant it.
How To Install:
- Start at the outside corner of the sidewall and align the first piece of step flashing with the bottom of the wall, folding the excess portion around the headwall.
Tip: If using aluminum, be gentle when handling it. Because it’s a soft metal, it rips easily.
- Working up from the bottom of the sidewall, install step flashing below each shingle, coming down at least one-half inch to three-quarter inch over the previous piece to cover nail holes.
- For the inside corner, cut step flashing down the middle of one side (from the longest edge toward the fold), then fold one of the cut pieces behind the other to form another 90-degree angle. Trim bottom edge of step flashing so that it extends just past the exposure (to prevent it from sticking out beneath the roof-to-wall flashing — see the next section for details).
- Use Zip System Tape (or Tyvek) to secure the step flashing to the OSB, creating a watertight seal.
After roll flashing and step flashing are installed, roof-to-wall flashing can be added to give a roof a beautifully finished look.
Roof-to-wall flashing is almost always going to be steel because it’s tough, Barringer says.
“The roof-to-wall that we do, it’s got a double-bolted bead at the bottom of it, so it sticks up a little bit, but that’s what reinforces it from the wind bending and denting it.”
Barringer says roof-to-wall flashing is pretty hard to mess up. The only thing you don’t want to do is anchor it to the roof instead of the wall because that would leave holes in the roof-to-wall flashing, which defeats its purpose, he explains.
How To Install:
- Cut roof-to-wall flashing to length and nail it to the headwall.
Tip: Barringer says you can seal nail holes if you like, but it’s not necessary. The Zip System Tape (or Tyvek) and roll flashing are behind the roof-to-wall flashing, so water should easily flow out beneath it.
When flashing is installed properly, it maintains the integrity of a roof, protecting against water damage. But what if the flashing isn’t done right? Would a faulty install void a shingle manufacturer’s warranty?
Barringer says manufacturers can’t guarantee anything when you’re using another company’s product.
“If you have bad flashing job, it’s not the shingles’ fault that it failed, it’s the bad flashing,” he says.
For more information about proper flashing installation, refer to pages 69-77 of ARMA’s Residential Asphalt Roofing Manual, 2014 Edition.
Plus, watch Mic Barringer and his brother Stevo demo installs in Atlas Roofing’s “Hammer Time With Paul” web series: