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Step Flashing vs Counter Flashing: A Comprehensive Comparison

August 30, 2023

In the realm of roofing and waterproofing, step flashing and counter flashing are essential components that work in tandem to provide protection against water intrusion and ensure the longevity of structures. These two techniques are commonly employed in areas where a roof intersects with a vertical surface, such as chimneys, walls, and dormers. While they serve the same purpose, step flashing and counter flashing differ in their design, application, and advantages. This article aims to elucidate the differences between step flashing and counter flashing, highlighting their respective benefits and best-use scenarios.

Step Flashing:

Step flashing is a series of individual metal pieces, usually made of aluminum, copper, or galvanized steel, that are installed stepwise along the junction between a sloped roof and a vertical surface. Each piece of step flashing is placed underneath the shingles or roofing material and overlaps with the adjacent piece to create a stepped effect, hence the name. This arrangement allows water to be diverted away from the joint and prevents it from seeping beneath the roofing material.

Advantages of Step Flashing:

Water Tightness: Step flashing provides excellent water tightness by creating a continuous barrier against water infiltration. Its stepped arrangement ensures that even if water manages to get behind one piece of flashing, it is directed down and away by the piece below it.

Flexibility: Step flashing is versatile and can be used with a variety of roofing materials, including asphalt shingles, wood shakes, and slate.
Aesthetics: When installed correctly, step flashing remains hidden beneath the roofing material, maintaining the visual appeal of the roof.

Counter Flashing:

Counter flashing, also known as cap flashing, is a complementary component that is typically made of metal and is installed over step flashing. Unlike step flashing, which is installed on the roof, counter flashing is integrated into the masonry or vertical surface. It is often embedded into the mortar joints or secured by lead anchors. The primary function of counter flashing is to provide an additional layer of protection against water infiltration and to conceal the upper edge of the step flashing, enhancing the overall aesthetic of the roofing system.

Advantages of Counter Flashing:

Enhanced Protection: Counter flashing acts as a secondary barrier against water, shielding the top edges of step flashing from direct exposure to the elements.

Durability: Since counter flashing is secured within the masonry, it offers increased durability and resistance to weathering, making it a long-lasting solution.

Aesthetic Appeal: Counter flashing can be designed to blend seamlessly with the building’s architecture, offering an aesthetically pleasing finish to the roof-wall intersection.

Choosing the Right Approach:

The choice between step flashing and counter flashing often depends on factors such as the roofing material, the design of the structure, and the climate of the region. In most cases, both step flashing and counter flashing are used in conjunction to provide comprehensive protection against water intrusion.

In conclusion, step flashing and counter flashing play pivotal roles in preventing water damage at vulnerable roof-wall intersections. Step flashing offers a primary line of defense, while counter flashing acts as a supplementary layer of protection and provides an elegant finish. When installed correctly, these two techniques work harmoniously to safeguard structures and uphold the integrity of roofing systems for years to come.

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