Did you know that experts have identified over 1,000 mold species in U.S. homes? And while an individual mold is tiny, it can reproduce quickly into a massive colony.
Once that happens, mold can contribute to poor indoor air quality (IAQ). That can cause health problems, such as allergies, asthma, and eye, ear, and nose irritation. The 20% of folks in the U.S. with environmental allergies are particularly at risk.
Your roof, in turn, can contribute to mold growth in your home, especially if it has faulty flashing.
But what is roof flashing in the first place, and how is it related to indoor mold growth? Why does your roof need flashing, and where should you install these materials?
We’ll answer all those questions and more in this roof flashing guide, so be sure to keep reading.
What Is Roof Flashing?
Roof flashing is a thin, flat metal sheet designed as a waterproofing material. It directs water away from roof joints, seams, and penetrations. These are the most leak-prone roof areas, considering they’re where different materials meet.
The Importance of Roof Flashing Explained
Roof flashing is crucial to keeping your home leak- and moisture-free. For one, it consists of metal, which is non-porous, so liquids can’t penetrate it easily. Thanks to that, it deflects water rather than absorbing or allowing it to seep.
Once deflected, the water then flows against the flashing material’s surface. From there, gravity pulls it toward the gutters or off the roof.
So if not for flashing, water can enter your home through the leak-prone areas of your roof. At the same time, failed flashing can also introduce moisture into your home.
Either way, water penetration from the roof can cause indoor dampness issues. Not only does that promote water damage, but it can also encourage mold growth.
Molds, after all, require only moisture, oxygen, and cellulose to survive. Cellulose is the primary constituent of many building materials, especially wood. So if they become damp due to leaks from roof penetrations, it won’t take long for molds to grow and feast on them.
What Are Common Roof Flashing Materials?
The three most common roof flashing materials are aluminum, copper, and steel.
When choosing between them, base your decision on the adjoining building materials. Choosing metal flashings compatible with them is vital to prevent galvanic corrosion.
Aluminum Flashing
Most aluminum flashing consists of light-gauge aluminum, a low-cost, malleable material. The latter makes it easy to form into various shapes to fit areas where flashing is necessary. Moreover, it tends to hold paint well, so you can easily pair it with the rest of your roof.
However, consider that lower-cost aluminum can pit in polluted air. Therefore, it may not be a good choice if you’re one of the 137 million people in the U.S. living in highly polluted areas.
Likewise, lower-grade aluminum can pit and oxidize in salty environments. In this case, you’d be better off with higher-grade versions or stainless steel.
Copper Flashing
Copper is malleable, strong, and highly resistant to the caustic effects of mortar. It’s also durable and resistant to hostile environments.
Moreover, copper has a natural antimicrobial property. Indeed, research has found pure copper can kill 99.9% of microorganisms within two hours. For the same reason, this metal is resistant to mold and rot.
However, it’s vital to note that unpainted copper oxidizes and develops a green patina. It’s a film that protects the underlying metal and, in some cases, can be attractive to some people. However, it can leave blue-green streaks due to runoff, staining nearby structures.
Galvanized Steel Flashing
Galvanized steel is a type of steel coated with zinc to protect it from corrosion and rust. It’s the least expensive of all metal flashing materials. However, it’s also the least durable and the worst choice for harsh climates.
Stainless Steel Flashing
Stainless steel is one of the top flashing materials as it’s very resistant to corrosion. For the same reason, it’s an excellent choice for homes in coastal and highly polluted areas. Unfortunately, however, it’s also among your most expensive flashing options.
What Are the Types of Roof Flashing?
Roof flashing is available in various types, each serving specific tasks. Moreover, their types indicate their shape or installation area. Some roof sections also require multiple types for optimal leak prevention.
Base Flashing
Base flashing is for jointed areas where the roof deck meets a vertical surface. An example is the bottom section of a chimney, where it intersects with the roof. Another is the lowest area of a dormer, usually below its sill.
Counter Flashing
Counter flashing is flashing placed directly above a base flashing. When joined, these two work together to channel water downward. They also go by the term “cap flashing.”
Continuous Flashing
Continuous flashing is a long, rectangular piece of metal. It channels water directly down to the roof area below. Some in the industry also refer to it as apron flashing.
Drip Edges
Drip edges are long, narrow strips of metal flashing placed along roof eaves or edges. They help divert water from the fascia, protecting the roof’s underlying components.
Drip edges overhang the sides of the roof. They also have small metal flanges that bend away from the fascia.
Kick-Out Flashing
Kick-out flashing is flashing material that connects the roof to the gutters. It “kicks out” water, diverting it into the rain-channeling pipes. You may also hear professionals in the roofing industry refer to it as diverter flashing.
Step Flashing
Step flashing is a rectangular metal sheet bent at an angle, making it resemble a stair step. Roofers usually install them in layers, say, between shingles or tiles. That design enables them to direct water away from the structure they cover, such as the sides of a chimney.
Where Exactly Is Roof Flashing Necessary?
Flashing is necessary for any roof area with a joint, seam, valley, or penetration. Likewise, it’s essential in places where two different roof materials meet. Depending on what you’ll flash, you may need several types.
Roof Valleys
Roof valleys are areas where two roof slopes meet. Flashing in these areas is essential since both pitches direct water into a valley. The valley then guides the water down to the gutters.
Because of their placement, valleys can gather lots of water, even during light rains. So, unprotected, they can allow water to seep into the underlying roof deck.
In most cases, valley flashing consists of long metal sheets shaped and sized to fit the valley. Roof panels, shingles, or tiles then overlap the flashing’s edges, creating a tight seal.
Dormers
Dormers are vertical windows projecting from a sloping roof. Since they often jut out high up on a rooftop, they require a separate roof section.
That jointed separation, in turn, calls for flashing on the areas where they meet the main roof.
Dormer flashing can take the form of multiple square metal pieces. Roofers add them between each row of shingles, tiles, or roof panels.
In other cases, the flashing can be a single, continuous strip of metal placed around the window. In this scenario, the flashing goes underneath the roofing material surrounding it.
Chimneys
A chimney is a type of roof penetration that needs various types of flashing to be fully leak-proof. They include a front cap flashing, a front base flashing, a side cap flashing, and a back cap flashing. Multiple pieces of step flashing are also a must for the sloping sides.
Skylights
Skylights are like dormers in that they’re also windows. However, they’re often more leak-prone since they’re a direct roof penetration. After all, they are types of glazed openings usually cut within a roof.
Surrounding skylights with flashing is a must to make them waterproof. Otherwise, they can leak water straight into a home.
In most instances, skylights need continuous side flashing. They also require a base, counter, and step flashing.
Roof Vents
Roof vents, also called stacks, are hoods and pipes jutting out rooftops. Some are for attic ventilation, while others are for plumbing systems. The latter is necessary for air pressure to escape out of plumbing systems.
Because vents are roof penetrations, they must feature a tight seal around the pipes. If they don’t, water can penetrate the punctured areas and cause damage to the attic or plumbing. Adding flashing to these openings can help keep them leak-free.
How Much Does Roof Flashing Cost?
Online estimates place the average cost of roof flashing at $14 to $25 per linear foot. However, your final bill depends on the flashing you need and its primary material. As mentioned above, galvanized steel is the cheapest, while stainless steel costs more.
Also, please remember that galvanized steel should never be in contact with copper. If they do, they will develop galvanic corrosion and put your roof at risk of failure.
That said, one of the best roof flashing tips is to use the same metal as your roof. At the very least, it should be compatible with the adjoining roof materials.
For example, it’s wise to use copper flashing and nails if you have a copper roof. On the other hand, always use aluminum fasteners for aluminum flashing.
When Should You Replace Roof Flashing?
According to the folks at Far West Roofing, the best shingle roofs last from 20 to 25 years. The good news is that roof flashing can last longer than that, as long as installed correctly.
However, if your current roof is already a replacement, you may have older flashing. In that case, you might want to replace the flashing too.
Don’t worry, as professional roofers will first inspect your entire roof. That allows them to determine if the flashing is still in good condition or is already failing.
If you’re getting a new roof, ensure it’s compatible with your existing flashing. If not, replace the flashing with materials that won’t induce galvanic corrosion.
Another solid indication you need flashing replacement is if any part of it is missing. Such often happens after severe weather, as strong winds can knock them loose and carry them away.
So, make it a habit to check the area around your house after a storm for roof parts that may have gotten blown away. If you see tiles, shingles, fasteners, and metal pieces, call a licensed roofer ASAP.
You may also likely need flashing replacement if you see signs of leaks by a fireplace or a skylight. Likewise, water penetration in the attic also indicates flashing failure. Please don’t delay having professionals replace the flashing in these situations.
When Should You Repair Roof Flashing?
If your roof flashing is only as old as your current roof, it’s still possible to repair its failing seals. And the best way to catch these problems early is to schedule your roof for annual checkups. Yearly inspections allow roofers to save existing flashing before they develop severe rusting.
You may also need to hire a roofer to reseal flashing materials if you see them pulling away from surfaces. For instance, you might notice sections of a kick-out flashing separating from a joint. Another example is if a chimney flashing breaks away from the vertical structure.
In any case, the sooner you have those problems checked, the higher the odds of them being repairable. That’s a plus since flashing repairs often cost less than removing and replacing them. That’s why you want to catch issues with them ASAP so that they don’t worsen to the point you need to change them.
Never Delay Flashing Repairs or Replacements
And there you have it, the ultimate guide answering the question, “what is roof flashing?” Now you know it’s a crucial metal component, protecting roofs from water penetration. After all, it acts as an extra barrier for roof joints, seams, valleys, and other penetrations.
For the same reason, it’s never a good idea to delay getting damaged flashing fixed or replaced.
Did you find this article informative? If so, and you want to read more, then feel free to stick around and check out our other latest news and blog posts!
