Need to know how to install flashing on existing roof? We’ve got the information you need to learn about flashing, its functionality, and how to install flashing on existing roof applications.

Flashing itself is quite simple – flashing can refer to any impermeable metal barrier used to prevent the ingress of water into roof systems, or to channel water and rain away from your home.

This makes high-quality flashing crucial to the overall health and well-being of your roof. So if your roof flashing is in poor condition, your roof could be at risk of water buildup, rot, and other expensive conditions that could require a roofing contractor to repair them.

To help you avoid costly roof replacements, we’ll go over the basics about metal flashing installation now, and help you replace roof flashing that’s gone bad with high-quality, durable metal flashing.

Understanding The Difference Between L-Shaped And T-Shaped Drip Flashing – What’s Best For You?

Essentially, both of these types of flashing do the same thing – they help guide water away from seams and joints in your roof, preventing water from soaking through your shingles, or in-between vulnerable joints.

L-shaped flashing is, as the name may suggest, shaped like an “L”, built with a simple 90-degree joint that flares out at the bottom. The L shape hugs the side of your roof tightly, while the flared base pushes water away from your siding, keeping your home more dry.

T-shaped flashing is slightly different. Shaped like an elongated “T”, this flashing attaches to the roof and projects outward, with a downward projection that sits an inch or two outside away for the side of your home.

The increased distance between your home and the flashing itself makes T-shaped flashing, a better overall choice when you’re going to install flashing on an existing roof. Water will run more smoothly across the flashing, and be pushed farther away from your home, helping you avoid excess moisture that can damage your siding.

Where Should I Install New Flashing?

Flashing is generally installed at any joints or edges in the roof where water could otherwise work its way in.

In order to properly install new flashing, you’ll have to remove the shingles surrounding your old flashing, and then re-lay them after installation. Typically, flashing is installed using roofing nails and roofing cement. After installation, you’ll then re-lay the shingles you removed, to provide a comprehensive, water-tight solution.

install flashing on existing roof

Flashing can be purchased in pre-formed styles to help you install it more easily, and these include:

  • Step Flashing – built to protect joints between roofs, chimneys, and other objects like skylights, this flashing “steps” up above the shingles and attaches to the object, providing comprehensive water protection.
  • Vent Pipe Flashing – as the name implies, this flashing is usually cylindrical, with a large, flanged based that allows you to lap it into your shingles during a roofing project.
  • Valley Flashing – This flashing is usually formed in a “V” or “W” shape, and is used where two different roof planes meet, forming a valley.
  • Drip Flashing – Also called drip edge, this type of flashing is installed on the edge of roofs, and helps guide water away from your roof and into your gutters.

Let’s take a deeper look at drip flashing now.

T-Shaped Drip Flashing – Overlap Edges To Let Water Drip

It’s best to overlap your T-shaped drip flashing shingle-style when you’re going to install flashing on an existing roof. Doing so will create a slightly declined effect that helps guide water away from your roof – if you install each piece of flashing “flush” to the next piece, you risk water pooling and getting into seams and cracks between the flashing.

It’s also best to overlap the eave metal in the direction of the prevailing view. For example, if the typical view is from left to right, reverse the order – place the right piece of eave metal under the right piece.

L-Shaped Flashing – Use Where The Wall And Roof Meet

Areas where the wall and roof meet can also use L-shaped flashing when you’re in the process of beginning to install flashing on an existing roof – installed correctly, L-shaped drip flashing is essential to a healthy roof.

Begin by removing the shingles at the affected area, and removing old flashing, if present. Then, nail the new L-shaped flashing under the builder’s felt, but above the fascia board.

Use roofing nails to install the L-shaped flashing flush with the roof and wall, then cover it with roofing cement, and reattach the roofer’s felt. Finally, reattach all shingles removed in the process.

Install Flashing On Existing Roof To Extend The Lifespan Of Your Roof

Whether your drip flashing has been failing and allowing excess water into your home, or your step or vent pipe flashing is corroding, learning to install roof flashing on an existing roof is a great way to maintain the health of your current roof.

If you need to install flashing on existing roof installations, but are unsure how, don’t worry – contact David Barbale home improvement services. David is a seasoned expert in the field of home improvement, including roofing, siding, flooring, and carpentry, and he can walk you through the entire process of how to install flashing on existing roof installations.

So don’t let your home fall victim to rain or moisture. Contact David Barbale today, and keep your roof healthy and happy, for a long service life.