Roof flashing guides rainwater away safely and prevents leaks by sealing the vulnerable gaps left by shingles. It redirects water runoff by channeling pooled or cascading water away from joints and onto the main shingle line. Installed under the shingles, flashing works out of sight to keep water moving in the right direction.
Where is Roof Flashing Installed?
Flashing is installed wherever the roof changes direction, meets a vertical surface, or has an opening for necessary accessories like vents or pipes. This includes:
Chimneys
Slylights
Vent and Pipe Boots
Sidewalls
Headwalls
Eaves and Rakes
Common Types of Roof Flashing
Flashing comes in all shapes and sizes depending on where it is being installed. The metal is bent and cut to create the strongest possible seal.
Step Flashing: Small L-shaped pieces of metal installed in a stair-step pattern along the slope where the roof meets a vertical wall or chimney. Directs water away from the vertical wall seam to keep it from getting behind shingles, preventing wood rot, mold, and interior water spots.
Base Flashing: The primary, bottom layer of metal installed directly at the base of a vertical wall. It runs up the wall to direct water away from the joint. Unlike step flashing, it is a larger, continuous piece of metal attached to the roof deck.
Counter Flashing: A secondary layer of metal installed over base or step flashing to keep moisture from working its way behind. It is attached to the vertical wall rather than nailed through the roofing deck. This allows the roof and wall to expand, contract, or settle without breaking the seal.
Valley Flashing: A V- or W-shaped piece of metal installed along the valleys where two roof slopes meet. It acts as a natural “highway” for water, directing heavy runoff, from rain or snow, off the slopes and into the gutter. This watertight barrier prevents water from seeping beneath the shingles and rotting the roof deck.
Drip Edge: Installed along the eaves and rakes to help direct water away from the roof and into the gutters. This helps prevent moisture build-up and rot in the fascia and roofing deck. In cold climates, it also helps reduces ice dams.
Pipe/Vent Boot Flashing: A small protective seal typically made of rubber, silicone, or hard plastic. Fits over plumbing or exhaust pipes wherever they penetrate the roof, and prevents moisture from seeping into the roof and home.
Kickout Flashing: A specialized diverter installed at the lower end of a roof-to-wall intersection that stops runoff from pouring straight down the wall, preventing wood rot, mold, and structural damage. Typically found near garage walls, dormers, and chimneys.
Apron/Headwall Flashing: A large L-shaped metal strip installed where the upper ends of roof slopes meet a vertical wall. It channels water running down walls to the shingles below it, preventing water from seeping behind siding, under shingles, or into the roof deck. Unlike step flashing on roof-to-wall joints, a headwall requires one continuous horizontal apron piece
Z-Flashing: A Z-shaped piece of metal installed along horizontal joints to channel water away from vulnerable seams. It keeps water from getting behind siding, windows, and doors, protecting the wall structure from rot or mold.
What is Flashing Made Out Of?
Flashing can be made from a variety of material but the most commonly found are:
Galvanized Steel: The most common choice for flashing. It is easy to work with, looks nice, and is highly resistant to corrosion.
Aluminum: The cheapest option, it is lightweight and easy to work with; however, it is not as durable or resistant to corrosion. It also needs to be coated when touching masonry or concrete as it degrades when exposed to alkaline surfaces.
Copper: While it is the most expensive option it is incredibly durable and can last a very long time. Is susceptible to weathering with a noticeable patina, which may be a deal-breaker to some homeowners. This is why you will see it around hard to see places such as chimneys.
How Does Flashing Get Damaged?
Flashing is exposed to the elements 24/7, and there are many ways its seal can be weakened. Knowing the common causes of damage can help homeowners act quickly and get ahead of the issue before problems arise.
Weather and Storm Damage
Hot and cold temperature cycles can cause flashing and roofing materials to expand and contact. This can damage the integrity of the seam over time.
High winds can lift or bend flashing, pulling them away from joints and other vertical surfaces.
Falling branches or large hail can dent or crack flashing.
Freeze and Thaw Cycles
Snow and ice can build up along flashing, when it melts the runoff can works its way under the flashing then lift it when it freezes and expands
Rust and Corrosion
Long exposure to the elements and the sun can wear down the metal over time. This rust and corrosion can cause brittle edges or small holes to form.
Sealant and Fastener Failure
Over time the caulk and mortar used can dry out and begin to crack, especially when exposed to extreme heat.
How Can I Tell if My Flashing is Damaged?
When homeowners have a roof leak, it can be hard to nail down the source. Luckily, flashing damage is usually accompanied by several telltale signs, both interior and exterior, that it’s time to take a closer look. Inside the home, look for brown or yellow water spots on ceilings or walls, especially near chimneys. Check to see if drywall feels damp or soft to the touch, or if paint has begun to bubble or peel. A noticeable musty odor is another common red flag, and following it can help uncover visible mold or mildew in the attic, usually around vents and windows. Outside, visually inspect the flashing. Rust and corrosion are a clear sign it’s beginning to wear down. Additionally, if there are noticeable dings or the flashing appears to be lifted, the watertight seal may be compromised.
Worried Your Flashing is Damaged?
If you are concerned your flashing may be damaged, it’s important to act quickly. Bad flashing is not an issue that resolves on its own, and finding the source of a leak early can save you thousands in repairs down the line. The best thing you can do right now is start with a visual inspection of the interior and exterior of your home, then call Lifetime Quality Roofing for a free professional inspection. Our team will pinpoint the problem and let you know whether a repair or replacement is needed. Never attempt to get on your roof or fix your flashing yourself, as it can be dangerous. Call us today or click below to schedule your free inspection.
