What Is Roof Flashing? 5 Types You Need To Know (2024)

Roof flashing is an element of your roof that protects it against leaks and helps you mitigate roof replacement costs. It is typically made of aluminum, steel or copper roofing materials.

“The piece of metal surrounds roof penetrations or areas prone to water flow, such as roof valleys, [which are] slopes in the roof,” said Niki O’Brien, operations manager at Custom Exteriors, an exterior remodeling company in the Denver metro area.

Roof flashing costs depend on the material. The least expensive option is aluminum, which ranges between $15 and $25 per square foot; then galvanized steel, at $18 to $28 per square foot; followed by copper, which is priced between $16 and $33 per square foot, according to estimates by Jon Sabo, founder of Mighty Dog Roofing, a professional roof company based in Omaha, Nebraska.

Read on for expert insight into roof flashing and how it protects your home.

What does roof flashing look like?

Nobody wants a leaky roof. No matter its location, a piece of flashing creates a “solid roof surface that is leakproof,” O’Brien said. When added into a series of flashing, roof flashing prevents leaks from happening.

But not all metal roof flashing needs to be apparent — the metal can match your roof’s color so the flashing isn’t an eyesore. “In newer installations, you will notice that flashing is colored to match the shingles and blend as well as possible,” O’Brien said. In older installations, the shiny metal is usually much more visible.

Chimney flashing

The continuous flashing or silver metal lining along the bottom of a chimney is predictably called chimney flashing. This type of roof flashing is at the base of the chimney and can prevent it from crumbling within the wall due to water damage.

Valley flashing

An open valley or slope can collect water and benefit from roof flashing. Valley flashing is the type of roof flashing that counters water buildup. It is placed along roof slopes, where two roof planes meet, to help rainwater drain down.

Step flashing

Step flashing helps seal water from creeping into spaces near dormer windows. This roof flashing may be adjacent to gutters and work as a splash shield.

Roof vent flashing

Flashing can also include metal added under roof vents to help direct water away from them. O’Brien said that roof vents are built with integrated flanges that act as flashing.

Skylight flashing

Skylight flashing creates a metal barrier around the junction between a skylight frame and the roof. This flashing helps divert water away from the skylight so no water accumulation can build up and leak into the house.

What metal is used for roof flashing?

Selecting the right roof flashing can depend on your budget. Aluminum flashing is the most affordable option. While copper flashing costs more, it does give your counter flashing (the vertical part of chimney flashing) some panache.

Aluminum

This roofing material is durable and can withstand inclement weather. “It is very lightweight, and it’s much more inexpensive than copper,” Sabo said. “However, if left unpainted, it can lead to corrosion, and it can also pit and oxidize over the years.”

Galvanized steel

Galvanized steel is used the most for roof flashing. “It is the least expensive but the least durable, which causes issues when it comes to holding up in harsher weather,” Sabo said. Galvanized steel can wear away, leaving it susceptible to corrosion. “Stainless steel is more expensive, but it is a longer-lasting product and is used in coastal areas.”

Copper

Copper is one of the longest-lasting but most expensive flashing materials. Copper does not corrode, making it very popular in areas with harsher weather. “Copper is also easy to mold, so it is easier to shape and work on any roof,” Sabo said.

Lead

Lead roof flashing is rarely used today but is one of the oldest roof flashing materials. “It actually has a life span of 200 years, but it must be handled right because it is a hazardous waste according to Resource Conservation and Recovery Act (RCRA) subtitle C requirements,” Sabo said.

Why do you need roof flashing?

Roof flashing is just another layer of protection against house leaks. Roof flashing will direct water runoff away from areas susceptible to leaks, stopping water damage and structural issues.

Because of the important role flashing plays in leak protection, it’s not really a DIY project.

Niki O’Brien

“Areas where the roof has been penetrated, or where shingles meet on two different slopes or butt up to a wall, are prone to leaks,” O’Brien said. For example, roof flashings work by allowing the sheet metal to continue so that the draining water flows mostly over the created surface.

Crevices along roof joints and areas where the roof shingles intersect are most vulnerable to roof leaks. Here is how roof flashing can stop the drips and damage.

Stops leaks

Skylights are the perfect example of a spot that needs roof flashing. This is especially true if its sealant has broken down due to age or the old flashing has corroded. With proper skylight flashing, the rain slides down the metal surface, down the shingles and off the roof. “Without that metal barrier, the water could find its way under the shingles and result in a roof leak,” O’Brien said.

Increases your roof’s life span

Roof flashing helps maintain the reliability of your home’s roofing system. Without leaks or water damage, the roof’s life span is longer, lowering the likelihood of expensive roof repairs or a replacement later.

Protects other roof features

Aside from the roof shingles and tiles, roof flashing can bolster and protect the features of your roof that can wear out over time. For example, correctly installed roof flashing ensures a watertight seal at intersections, which are places where the roof meets other roof features, O’Brien said. That means walls, chimneys or vents are protected.

Adds curb appeal

Metal roof flashing can be made from an array of materials. Copper, for instance, oxidizes over time into a greenish patina. While copper can be more expensive than other metals, it is a material that has been used in roofs throughout history. Thus, the material could give your home an Old World or classic look.

Gives you peace of mind

If you are considering selling your home, a superbly cared-for roof in good condition will ensure your home value doesn’t dip. Roof flashing will help protect your home’s roof and add to your property’s overall salability.

While there is no direct link between roof flashing and your home’s ROI, you have peace of mind knowing that leaks are less likely to occur. “You will know that the roof is shedding water appropriately and not onto your baby grand piano,” O’Brien said.

What are the signs that roof flashing is compromised?

Lack of roof flashing or compromised flashing creates water leaks that go undetected until it’s too late. “Most homeowners don’t even notice issues with roof flashing before a leak shows up inside the home,” O’Brien said.

“Rust is usually the No. 1 sign of flashing needing to be replaced,” Sabo said.

If you suspect you have damaged roof flashing or need roof flashing to begin with, you should call in a professional roofing company as soon as possible, O’Brien added. “The longer you wait, the more likely you are to experience a leak, which can lead to leaks, water damage, or mold,” she said.

Rust is usually the No. 1 sign of flashing needing to be replaced.

Jon Sabo

What’s next?

Installing roof flashing is a job for a professional. If you think your roof could use new flashing, contact a reputable roofer or contractor who has worked with different roofing materials. “Because of the important role flashing plays in leak protection, it’s not really a DIY project,” O’Brien said.

Find three roofing experts in your area to compare prices and ask to receive some reviews from their former clients. Always check you are working with a licensed and insured roofing professional.