The roof flashing is a critical part of your roofing system. It prevents water from seeping into vulnerable areas, protecting the structure and extending its service life.
Begin the flashing installation process by installing shingles up to the first piece of step flashing along the sidewall. Nail and seal this with roofing cement.
Step Flashing
Step flashing is applied where the roof meets the side walls of dormers, chimneys and some skylights. It is also used around doorways, windows and some vents. It is typically made of rust-resistant metal and can be purchased in pre-cut pieces or cut from longer strips. Each piece should be at least 10 inches long and at least 2 to 3 inches wider than the shingle exposure it is covering. It should be nailed to the wall and not the roof deck as building movement can cause gaps in the roofing shingles where water can seep in.
Installing step flashing is a bit more complicated than installing base or counter flashing. First, lay an ice-and-water shield on the roof deck and apply felt paper underlayment. Then, lay a whole shingle course up to the first piece of step flashing. Then, apply a bead of caulking around the edge of the step flashing to seal it. Next, apply a second piece of step flashing that overlaps the first by at least 2 to 3 inches and nails it to the roof deck using roofing cement. Finally, nail a shingle to the top of the flashing and tuck it under the shingle below.
Next, a kickout flashing is installed at the end of the step flashing to guide the water toward the gutter and away from the house wall. It kind of looks like an L-shaped scoop and helps to ensure that the water doesn’t just run along the shingles or down the wall itself.
A final piece of flashing, called a “counter” is then hung on the indentation left by the chimney and nailed to the roof deck with roofing cement and two nails. The counter flashing should hang at least 4 to 5 inches past each edge of the chimney. Once the counter flashing is in place, a bead of caulking can be applied to close the gap between it and the chimney.
Corner Flashing
If your roof features a wall that intersects with the roof (such as the corner of a dormer), you’ll need to install special flashing. This type of flashing can be purchased prefabricated from specialty roofing suppliers. This is a great time-saver because it eliminates the need to fabricate your own flashing out of shingle tins or sheet metal. It also eliminates the need for roof cement, which can leave potential leaking holes.
To create your own flashing, first apply a layer of roofing underlayment to the area where you’ll be installing the corner flashing. Then, nail a piece of step flashing to the roof where it will meet the wall. You’ll want to ensure that the flashing extends past the edge of the wall to cover the entire intersection of the wall and the roof. If you’re having trouble finding a flashing that will cover this area, you can use a piece of flat aluminum stock cut to size. It’s important to choose a material that won’t degrade from exposure to sunlight or other environmental conditions.
Once you’ve laid down a piece of step flashing, install a shingle above it. Make sure the shingle is nailed in securely, as any movement could cause water leaks. Next, apply a second piece of flashing, this time on top of the corner flashing. Make sure it overlaps the previous flashing by at least 3 inches. Finally, add a shingle at the top of this flashing section, which will eventually be covered by ridge flashing.
Another application for flashing is around vent pipes that run through the roof. You can install a flashing collar around the pipe, which will prevent leaking and direct water flow away from the roof’s surface. When choosing a flashing collar, it’s important to make sure that the collar opening is sized to match the pipe’s diameter. Otherwise, the collar will wear out prematurely and leave you with a potential leak spot.
You can also install a counter flashing on the opposite side of the vent pipe to help seal the chimney and prevent leaks. The flashing should be nailed in place with roofing nails spaced every 2 inches. Be sure to spread a generous bead of roof sealant along the edges of the flashing before driving in the nails. You should also test the flashing by running a hose on your roof to see if it sheds water properly.
Kickout Flashing
Kickout flashing, also known as diverter flashing, is a specialized type of roof flashing designed to handle a very specific problem. It is installed where a gutter ends adjacent to a wall and helps to prevent water from running down the sidewall and into the house, which can lead to significant rot and water damage inside walls and at the foundation of a home.
When installing kickout flashing, homeowners need to first make sure that the wall has a corner on it. If it does, install the corner flashing, as described below, before continuing with step flashing.
Next, homeowners need to install a piece of step flashing at the base of the wall. They should then install the shingle course up to where the corner flashing begins.
Finally, homeowners should use roof cement on the underside of the first shingle and nail it to the flashing. This will ensure that the shingles will stay in place and will not be blown off by the wind.
Once the first shingle is nailed to the flashing, it is time to start installing the other shingles. It is important to make sure that the shingles do not cover the top of the flashing, as this can cause leaks. Homeowners should also be sure to tuck the shingles under the flashing and over the edge of the gutter.
If you are installing a vent boot, you will need to install a piece of kickout flashing (also called a diverter flashing) to help prevent rainwater from entering the boot. This specialized flashing is typically made from a malleable, molded one-piece TPO material that can be easily formed into shape. These types of flashings are often far superior to field-made pieces that have been cut and bent from metal coil stock, which usually leak or are too small.
Although roof flashing may seem like a minor component of a roofing system, it is essential for preventing leaks. It is especially critical for areas with low points, where the roof meets walls, roof edges, and roof protrusions. Without adequate flashing, these areas would be susceptible to water leaks, which can lead to serious and costly damage to the home.
Ridge Flashing
Roof flashing may not be the most visible part of your home, but it protects the underlying structure from water damage and leaks. It creates a tight seal around vulnerable areas where the shingles butt up against a wall, chimney, or other protrusion, and it redirects rainwater away from the structure. Properly installed, it keeps moisture out for decades, and it prevents leaks in high-risk areas.
When a roof leak occurs, moisture can creep under the shingles and cause severe water damage. It can also reach the insulation and drywall, leading to mold and mildew. If left unattended, mold and mildew can lead to health problems. The best way to keep your home safe and healthy is by addressing any leaks as soon as they occur. That’s why it’s important to understand how flashing works, and how to properly install it.
Typically, roof flashing is made of metal, including copper, zinc, or aluminum. It’s available preformed to fit general specifications, or it can be hand-cut by a contractor to suit a particular roof design. Flashing is also available in a variety of colors and materials, to match the color and style of your roof and house siding.
To install flashing, start by cleaning the area and removing any debris or old flashing material. Next, measure and cut the flashing material to size using a set of tin snips or scissors. Position the flashing and secure it with roofing cement or other waterproof sealant. Usually, it’s a good idea to overlap the flashing by at least 2 to 3 inches. This helps to ensure that the flashing is completely protected by the shingles and waterproof underlayment.
Once the flashing is in place, a shingle should be placed on top of it. Depending on the type of flashing used, it’s sometimes a good idea to reinforce the seams with flashing tape to increase its longevity. Once the shingles are in place, a simple water test should be performed to ensure that the flashing is leak-proof.
Roof flashing is a vital component of any roof installation, and knowing how to properly install it can help you avoid costly water damage. It’s a project that most homeowners should leave to the professionals, but if you are a do-it-yourselfer, these tips will help you make a safe and effective flashing installation.