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Roof flashing materials are weather-proof.  You may see roof flashing made from plastic, rubber or felt, but it’s usually a rust-resistant metal such as:

• Galvanized steel – used most often and preferred by professional roofing companies.

• Aluminum-zinc coated steel marketed under the Galvalume name – offers more corrosion resistance than galvanized steel

• Aluminum – easily bent and the material of choice for DIY installation

• Copper – custom-made for copper roofs

Roof flashing is installed wherever there’s an intersection or a termination of your roof. That means you’ll see roof flashing material in the following areas:

• at vent pipes

• along roof ridges

• in low areas (valleys) where roof pitches connect

• around dormer walls

• around skylights or other windows extended from the roof

For flat roofs or those without overhanging eaves or soffits, drip edge flashing may be installed to move water off the roof into a gutter system.

Flashing Damage: Leaks Waiting to Happen

Because flashing protects some of the most vulnerable parts of your roof, any damage to flashing is cause for concern.  When flashing cracks or is bent upward, moisture is able to run inside to the roof seams.  This poses an especially large problem during heavy rains.  While your roof is protected by underlayment (a membrane or roofing felt), some roofing materials will deteriorate if faced with ongoing moisture.  This will cause a leak to form.  Moisture damage is particularly annoying because it may run inside the flashing and create damage far away from the entry point.  A full inspection of flashing is often needed to pinpoint the leak’s origin.

Assessing Roof Flashing Damage

Since roof flashing is usually made with metal, it appears to be sturdier than shingles or tiles.  It is designed to be tough.  But over time, roof flashing material can show signs of wear and can be damaged by acid rain, wind, hail, severe heat and heavy snows. In coastal areas, exposure to salt air can also affect roof flashing.  Take time to visually check your roof after a severe weather event. Inspect your roof in the spring to evaluate any damage from the winter.  Review it again in the fall to determine if repairs are needed before another winter arrives.  While your visual inspection from ground level is a good starting point, consider hiring a professional roofer.  Their expertise ensures damage will be found, and they’ll provide recommendations for thorough repairs.

Signs of roof flashing damage range from minor, hard-to-spot trouble areas to major breaches requiring significant repair.  Here are some issues to look for.

• Small holes: Water needs only a little space to seep under roof shingles.  Small holes in roof flashing caused by corrosion or wildlife (woodpeckers) can turn into a large problem and need to be sealed.

• Rust or corrosion: Even with galvanized coatings, roof flashing materials will corrode over time due to the reaction with air.  Salt air is more corrosive than inland air.  Rusted roof flashing will no longer repel water and needs to be cleaned, sealed or replaced.

• Missing pieces: If roof flashing loosens during storms or high winds, is not affixed properly or is peeled back by a curious raccoon, you may notice missing pieces.  The absence of the water barrier flashing provides makes this a high priority repair.

• Bends, cracks or dents: A bend or crack seems minor, but this type of damage breaks the galvanized coating on steel or weakens the structure on other metals.  When the metal is compromised, it can be more susceptible to corrosion.

• Internal leaks: You may not be able to see all the roof flashing, but internal leaks near windows, fireplaces, skylights or in your attic are another sign of damage.

• Mold or staining on fascia boards: Drip edge flashing that was improperly installed can cause this type of damage.

• Worn or damaged siding or shingles: When the roof flashing fails to rebuff water properly, you may see water damage on siding.  Shingles in low spots or near areas where flashing is used may show signs of water damage (darkening, bending), indicating the roof flashing material has been compromised.

Where Flashing is Installed

How flashing is installed depends on where it is installed.  The most basic type of flashing is the flashing that collects water in the valleys of your roof.  These are the joints where two slopes meet. Flashing in these areas will be installed underneath the shingles on either side.  When water reaches the valley, it will flow off the shingles and into the gulley created by the flashing.  From there the water is safely directed to a gutter, downspout, or simply off the edge of the roof.

Chimney Flashing

Another common location for flashing is around a chimney.  Chimney flashing is actually a collection of several types of flashing.  Continuous flashing, a single strip of metal (or another material) is installed along the base of the chimney where it meets the roof.  Along the sides of the chimney, step flashing is installed.  This consists of squares of flashing that overlap, similar to shingles, and climb up the side of the chimney along with the slope of the roof.

Saddle flashing is like a little mini roof behind the chimney on the higher side.  Also called a cricket, this is a ridged design feature. It directs water and debris to either side of the chimney. That way it does not backup and collect on the high side of the chimney.

Finally, where the top of the flashing meets the brick (or other material) of the chimney, cap flashing will be mortared or caulked to the chimney.  This flashing is attached to the chimney at its top and its lower part overlaps the flashing below.  The bottom edge of the cap flashing is molded to direct water outward and away from the step flashing.  It keeps water from seeping behind the step flashing.

Other Locations for Flashing

Flashing is also used around vents in the roof.  The type of flashing depends of the type of vent.  This flashing is also commonly included with the vent hardware.  The same is true of skylights.  Skylights require flashing around the area where they meet the roof.  The flashing is often integrated into the design of the skylight.  If it is not, flashing must be installed to prevent leaks around the skylight.

If a house has dormers, flashing will be required where the vertical walls of the dormer meet the sloped roof.  Like with a chimney, stepped flashing is installed along the vertical wall of the dormer following the slope of the roof.  The step flashing will be capped with cap flashing that is attached to the exterior of the dormer.  The base of the dormer will get continuous flashing and the peak of the dormer will get saddle flashing.  The area where the roof of the dormer meets the rest of the roof will be treated like other valleys, with standard flashing that rests beneath the shingles on either side.

Membrane Shrinkage

Over time, dimensional shortening of the roof membrane can result in shrinkage.  As the shrinking occurs, it creates pressure on the flashing and roof seams.  Since this shortening, also known as tenting, cannot be repaired, eventually the flashing and seams are going to burst.  Where the flashing is no longer protecting the roof of the building, water can gain entry, creating more issues with the roof if it isn’t addressed immediately.

Poor Repair Jobs

Regular roof maintenance is essential to the life of your  home.  It should be inspected regularly, because once an issue is caused by the elements, it’s likely going to get worse.  Homeowners should always hire a professional to address issues related to the roof and its flashing.  Flashing installation requires many important steps and knowledge that business owners and their maintenance employees typically don’t have.

A poor repair job could lead to leaking or billowing, which happens when parts of the flashing become disconnected from the structure and eventually become even more damaged in high wind.  Even worse, a bad repair job can also lead to part or even all of the roof blowing away.

Age

Flashing isn’t made to last forever.  Seasonal temperature fluctuations can cause roof flashing to warp.  Flashing can also bend as the building settles, and it can rust with age.  Old flashing experiencing any of these issues is likely to fail the materials it is designed to protect.  If the flashing is aged, the entire roof probably is as well.  How often your roof and its flashing should be replaced depends on the type of roof the building has.  Generally, an asphalt roof will last 20 years, while a metal roof can last up to 30 years.

Accidental Damage

Sometimes a person performing an inspection or repair on the roof can accidentally and unknowingly cause damage to flashing.  It’s important that anyone stepping onto a roof knows what they are doing as they begin to walk around.  Damage to flashing can occur when someone steps on it the wrong way.  If the flashing becomes dented or cracked, it can give way to water.

Roof flashing is a small but important component of a roof.  If you suspect your flashing has become weakened or damaged, always consult with a professional roofer before it leads to a larger issue.