Why Step Flashing Matters: Safeguarding Your Roof's Integrity

Every homeowner and roofing contractor understands the pivotal role that roofing systems play in the protection and integrity of a home. One of the essential components that ensure this protection is a little-known element called "step flashing". Step flashing is an essential part of roofing that keeps your home protected from water damage. Even though it is not commonly talked about, it is important to know its significance.

Understanding Step Flashing


Step flashing is a roofing technique that safeguards the meeting point of your roof with the sidewall of your building. It's particularly crucial because these areas are especially susceptible to water leakage during rainfall, which can damage your roof and lead to the growth of mold and mildew.

The name 'step flashing' comes from how it's installed — it's put into place in a step-like pattern alongside the shingles of the roof.

Each piece of step flashing is a strip of metal, usually made from aluminum, galvanized steel or copper, that's bent at a 90-degree angle. It is installed in the joint between your roof shingles and the adjoining wall to prevent water from seeping through.

The Function of Step Flashing

One of the fundamental truths about any roof is that any joint or seam presents an opportunity for water to find its way in. Think about the place where your roof meets a wall, maybe above a dormer window or next to a chimney. Water coming off that wall or structure will collect in the right-angle intersection between the wall and the roof. This is where step flashing becomes invaluable.

As homeowners, you might be tempted to rely on caulking, tar or other liquid products to seal these junctions. However, such methods tend to provide only temporary solutions. Over time, these sealants may fail, letting water seep into your home.

On the other hand, step flashing, with its rigidity and flexibility, provides a long-lasting solution. It moves with the home as it expands and contracts yet it is sturdy enough to prevent water ingress.

Other Types of Flashing on a Roofing Project

These are the most typical installations of roof flashing:

Counter Flashing

To flash chimneys, roofing contractors use counter-flashing which consists of two pieces of flashing. First, the base flashing is fixed around the bottom of the chimney. Next, the counter-flashing is installed on top of the base flashing and firmly set in the chimney's masonry. The purpose is to block water from seeping in behind the base flashing. Regardless of the use case, using a second piece of flashing is always required.

Plumbing Vent Boot Flashing

A vent flashing is a type of flashing that encircles a vent in a cylindrical shape. The shingles are then placed over a base or boot that covers the flashing. The boot's height is designed to divert water away from the vent as it runs off the roof.

Skylight Flashing

Skylight flashing is normally provided as a kit by the manufacturer of the skylight. This is to ensure that no leaks will be present when the job is complete. The flashing kit is custom designed to fit each skylight model and helps to ensure no mistakes if the directions are followed.

Installation of Step Flashing

Do not nail through the sidewall when installing step flashing. Nail through the shingle making sure the nail head is covered by the shingle that goes over it.

1. Install the First Flashing Piece

Step flashing starts with the first layer of shingles that meet a sidewall or other vertical surface. Take your first piece of step flashing and secure it to the roof with a roofing nail. Make sure it extends at least 2 inches (5 inches is best) up the sidewall and overlaps the previous piece by at least 2 inches. Do not nail through the flashing into the sidewall as the step flashing needs to be able to move due to expansion and contraction.

2. Continue in a Weave Fashion

Continue to install each subsequent piece of flashing in a weave pattern. This means each piece should overlap the one below it and be placed under the shingle above it. It's essential to follow this pattern in order to properly seal your sidewall.

3. Cut and Bend Flashing at Roof Peak

Once you've reached the rooftop, cut along the fold line of the flashing piece and fold the bottom flap downwards. Secure it in place with a roofing nail or staple.

4. Finalize the Installation

After installing all the pieces, apply a vertical bead of sealant to the piece you installed on the first side of the peak. Cut the final piece along the fold line, bend its flap down and press it onto the first piece. Finally, hammer one nail into the wall to secure the final piece.

5. Inspect the Work

After installation, inspect your work to ensure that all pieces are securely in place and that the flashing is properly layered to direct water away from the roof and building.

Keep in mind that this is a basic guide and the specifics may vary depending on the type of roofing material, the roof's slope and the specific construction of the building.

Always follow local building codes and manufacturer's instructions. If you're unsure, consider consulting with a roofing professional to ensure proper installation.

Potential Damage if Step Flashing is not Used

Roofs need step flashing to prevent water damage. Moisture intrusion can lead to mold, rot and structural failure, and it can attract pests. Step flashing, when correctly installed, provides an effective defense against these threats.

Moreover, step flashing is not just about protection — it's also about longevity. Step flashing is a long-term solution that, once installed, provides continuous protection against water intrusion for the lifetime of the roof. It reduces the need for constant repairs and can save you a considerable amount of money in the long run.

Remember, step flashing might be a small detail in the grand scheme of a home, but its role is vast and irreplaceable. Neglecting it can have severe consequences and appreciating it can lead to safer, drier homes.

Choose Alsco® Metals for the Highest Quality Step Flashing Materials


For homeowners looking to protect their property from water damage, Alsco Metals provides the highest quality step flashing materials on the market. Our durable, long-lasting products are designed to move with your home as it expands and contracts while providing superior protection against water intrusion. We also carry other roofing, siding and trim products to help protect and beautify your home.

Contact us today and speak with one of our professional advisors!