Flashing is a vital part of your home's exterior, but the many varieties can be confusing. We'll look at the most common types, and how they work.
Most Common Kinds of Flashing and How They Work
Have you ever heard a contractor or other DIYer talk about “flashing” and wondered what they mean? Or maybe you’ve got a rough idea but need clarification on the number of flashing types available. Well, no need to worry — master tradesman Geoff Walker of ASAP Restoration has helped us assemble a list of the most common types of flashing that DIYers encounter.
On This Page
What is Flashing?
Flashing is a term used to describe a water-resistant material (most often metal) used to reinforce the seams between the different layers of your home’s exterior. Flashing is inexpensive, goes on easily, and can save you—and your home —a ton of moisture-related headaches down the road.
There are many different types of flashing. Some can be used in many different locations, while others are intended for very specific applications. Most types of flashing are named either for their appearance (like Z flashing) or for where they are installed (such as valley flashing).
Base Flashing
Base flashing can refer to any type of flashing that sits at the base of an opening or penetration. It’s combined with one of the other types of flashing to provide a robust defense. While it may be preformed, it may also start as a plain roll of flashing before being sculpted into a custom form.
“Base flashing is simply a piece of metal that has been bent into a specific shape,” says Walker. It’s typically combined with another layer of flashing on top of it. It can redirect water accumulation away from any vulnerabilities in the home’s exterior.
Step Flashing
Step flashing is bent at a right angle, like a capital L. It’s used when there’s a 90-degree junction with a roof, such as at the side of a dormer or wall. One side of the step flashing goes up the wall, and the other extends horizontally onto the roof. Step flashing is typically laid out along the roof/wall junction in an overlapping pattern, like roof shingles.
Counter Flashing
Any type of flashing that sits on other flashing to prevent water penetration is known as counter flashing. For example, picture step flashing sitting at the junction of a chimney and the roof. The side of the step flashing extends upward along the brick face of the chimney. But water can still get into that small gap between the brick and metal flashing. By placing the chimney counter flashing on top of the step flashing, the water is shed away from the chimney and onto the step flashing.
Drip Cap Flashing
Drip cap flashing is another L-shaped flashing, but is installed over windows and doors. One leg of the “L” goes over the window or door brick mold, while the other lies behind the siding that will go above.
Drip cap is put in place after the window or door is installed and before the siding is installed. Some windows and doors that have uni-body or molded frames have their own form of built-in drip cap and don’t require any additional drip cap flashing.
Drip Edge
Not to be confused with drip cap, drip edge is installed along the edges of a roof, below the shingles. Sometimes called a “gutter apron,” it ensures that every drip makes its way into the gutters rather than flowing back up the underside of the last row of shingles.
If you look at the drip edge profile, you’ll see it’s essentially a metal lip with an additional ridge on its underside. When water flows off the singles onto the drip edge, it may begin to roll back up the underside toward the roof’s vulnerable sheathing. That ridge on the underside redirects that flow, giving the water an escape route and redirecting it to the gutter system.
Valley Flashing
“As the name would indicate,” says Walker, “valley flashing is used in the areas where two roofing elements meet and form a valley between them.”
If you look at a roof where two rooflines meet, you’ll typically find that the resulting valley has exposed metal flashing. Called an “open valley,” that metal valley flashing acts like a high-speed roadway for water, allowing it to shed quickly and efficiently. (Closed or woven valley designs look and function differently, but that’s a topic too broad to cover here.)
Valley flashing usually has a distinctive peak in the middle of the valley to help channel water and prevent it from pooling.
Boot Flashing
Boot flashing, explains Walker, “is a circular piece of flashing that goes around vents and prevents water from intruding at that connection point.”
It’s typically a rubber and/or metal piece that slips over the vent, like a boot. Pipe penetrations are a common source for roof leaks, and replacing boot flashing (sometimes called a pipe boot) is a relatively easy DIY fix.
Z Flashing
Z flashing gets its name from its side profile, which resembles the letter Z. It sits on top of another material, creating a cap over that material to allow water to shed off. It’s frequently seen on deck ledger boards or other areas where a material protrudes beyond the home’s siding.
Flashing Tape
Not all flashing is made of rigid metal. Flashing tape is designed for easy installation around penetrations, adding another layer of protection against cold and water. You’ll frequently see it used around door or window openings.
About the Expert
- Geoff Walker is a company superintendent and an expert in all things construction at ASAP Restoration. With more than 47 years of experience in the construction and restoration industries, Geoff has traveled the world, learning and perfecting his skills in the trade.
