What Is Roof Flashing? (Function, Cost, & More)

by Nov 15, 2023

Roof flashing is a vital component of your roofing system. To function properly, your roof depends on the flashing to have been installed properly and remain in good condition. 

Of course, most homeowners don’t really know what roof flashing is — which means they also don’t know when it’s time to have it inspected or replaced. 

Homeowners who don’t keep up with the various components of their roofing systems, especially the roof flashing, will eventually have to deal with water damage and the cost of repairing said damage. That’s why we’re going to discuss everything a homeowner should know about their roof flashing, including signs of damage, costs, and more. 

Keep reading to learn more about how to repair your roof and flashing.

Roof Flashing Explained

red roof with new flashing

So, what is roof flashing?

Roof flashing is the thin piece of galvanized metal that’s installed around your roof’s drip edge and other components, such as:

  • Chimneys
  • Skylights
  • Valleys
  • Vents

The purpose of roof flashing is to redirect water flow off of your roof to prevent moisture from seeping into any openings or cracks around vulnerable areas. This would include the area where the base of your chimney meets the roof decking and shingles, for example.

As far as the sheet metal used to make roof flashing, aluminum is the most common material. It’s the most affordable and durable of all the roof flashing materials, however, you’ll also find that the sheet metal also comes from galvanized steel, copper, and other metal amalgams. Their durability is also directly related to the other roofing materials used — for example, a copper roof will typically require copper roof flashing for a more seamless aesthetic and to maintain the overall structural integrity of the roof surface.

Generally speaking, metal flashing should be thought of as your roof’s most critical component when it comes to protection from the elements. Without it, your entire roofing system would be incredibly vulnerable to leakage and moisture build-up, which can lead to costly issues such as wood rot, mold, and rapid deterioration.

Types of Roof Flashing

While all the metal flashing on your roof serves the same purpose, it’s important to understand that there are several different types of roof flashing. The various types of roof flashing are categorized by the part of the roof they’re installed with, with the most common types of roof flashing being:

  • Base flashing: Base flashing is used around the chimneys of a roof. Chimney roofs usually need pieces of flashing to ensure waterproofing around the base of their components. 
  • Step flashing: Step flashing refers to rectangular metal flashing that’s bent at a 90-degree angle in the middle to create a water-repelling pathway. This roof flashing is installed in multiple layers to prevent the roof’s walls from absorbing water by leading that water in the opposite direction.
  • Valley flashing: Valley flashing is always installed around the open roof valleys and works by channeling rainwater off the roof and into the gutters. This roof flashing also prevents the buildup of debris that tends to collect during storms and heavy winds.
  • Drip edge flashing: Drip edge flashing gets installed around the edges of the roof — otherwise known as the roof’s drip edge. This flashing moves rainwater off the roof which prevents excess moisture from getting into the starter shingles and causing them to rot and deteriorate.
  • Vent pipe flashing: Vent pipe flashing is installed around the base of your roof’s vent pipes. This flashing is meant to seal the ventilation pipes, which keeps out drafts and prevents leaks and water damage from occurring in that area.
  • Continuous flashing: Continuous flashing is the long metal sheet that’s installed on the roof’s surface, just beneath the shingles. Continuous flashing directs water flow over to the roof’s edge and straight into the gutter, and it’s most commonly found on asphalt shingle roofs.
  • Counter flashing: Counter flashing is installed on top or opposite of the base flashing. Counter flashing is what prevents water from seeping into the roof’s shingles as well as the chimney.

How Much Does Roof Flashing Cost?

close up to worker repairing roof flashing

The average cost of roof flashing ranges between $15 and $25 per linear foot. When calculating the cost of materials per linear foot, most roof flashing repairs end up costing between $200 and $500, while a complete roof flashing replacement can cost $1,500 or more — depending on the number of roofing components you have.

Of course, the ultimate cost of replacing your roof flashing will also involve certain factors, including the installation and roofing materials required. Your roofing contractor may also discover other issues during their initial inspection, which means you may have a more complex and costly repair job on your hands. 

The other factors that your roofing contractor will take into consideration when writing up an estimate will also include:

  • Flashing material
  • Size of the area that requires new flashing
  • The extent of any damage your roof has to its existing flashing and other components
  • Chimney size and type
  • The configuration of your roof
  • Detailed inspections (not all roofers provide free inspections)
  • Cleanup

Signs It’s Time For New Roof Flashing

It can be challenging to determine on your own whether your roof is in need of flashing repairs or completely new flashing. The most obvious signs to look out for include:

  • Rust stains on the firebox of your chimney
  • Water stains on upper level ceilings and walls
  • Water leakage in your attic or access space
  • Corrosion or rust holes in areas where flashing is visible

Rust is typically the primary sign that your roof’s flashing is in bad shape. If you notice rust when looking up at your roof or any of the other signs that your flashing has gone bad, you’ll want to get in touch with a trusted roofing professional immediately to determine the extent of the damage. 

As a homeowner, you need to address roofing issues — especially damaged roof flashing — right away. Otherwise, minor issues will quickly become major issues that threaten the structural integrity of your roofing system and home, which will end up costing you a lot more in the long run.

Have you noticed the signs of bad flashing on your roof? If so, schedule an appointment with the roofing specialists at Alamo right away!

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