How to Install Flashing Under Siding

building house on blueprints with worker - construction project

As our homes are continually exposed to the elements, keeping everything in working order is key. There are various systems in place to help protect what’s inside your home from what’s outside when installed properly.

Your roof plays a big part, as does your siding. But did you know there’s an extra layer of protection you can give your home to prevent elemental damage?

Exterior flashing is a system that works with your siding and roof. It’s designed to provide an extra barrier on top of your home’s structural elements. Think of it like how food packaging keeps food shelf-stable for longer than if it were left out. In practice, exterior flashing can help protect against weathering and decay as your home is battered by rain, snow, and wind.

There are countless reasons to consider installing flashing for siding on your home. But before learning how to install roof flashing against siding, we need to back up. Let’s first better understand flashing as a concept and what materials work best.

What is Flashing Made From?

You have likely seen exterior flashing on a house’s roofline. This flashing style is typically exposed above the shingleline. And it is typically found as a series of folded pieces of metal flashing for siding-roof junctions.

Unlike roof flashing, which is commonly done with materials like copper and aluminum, siding flashing is not exposed. A roof flashing installation needs to protect and add to a home’s curb appeal. But siding flashing is purely about protection.

Siding flashing is typically done with a thin layer of water- and corrosion-resistant material. It can be made from acrylic, rubber, or even rubberized asphalt. Metal flashing for siding can be used; however, this material is not common.

The Basics: How to Install Flashing Under Siding

Now that we know the value flashing can provide, let’s discuss how to properly install it. As noted, flashing site underneath your home’s siding. However, there are many layers to a home’s exterior, and the placement of the flashing in the stack is critical.

When installing siding flashing, it (and the counterflashing) should be placed between the house wrap and the underlayment. Essentially, each layer of the house should step down so that water cannot penetrate. When done correctly, water should simply drip down from one layer to the next in order until it reaches the ground or a gutter. It should drip, in order, from:

  1. Siding
  2. Counter-flashing
  3. Flashing

Side Note: How to Install Flashing Under Existing Siding

If you own a house and need to install this system for yourself, here’s how to install flashing under existing siding:

  1. Loosen and lift your pieces of siding where they meet any butt joint on your house.
  2. Slide a cut piece of flashing under the existing siding. Ensure that you have loosened your siding enough to slide the siding flashing all the way under it. You should not see any flashing sticking out under the bottom edge.
  3. Fasten your flashing to your house with nails or staples.
  4. Re-nail your lap siding back over the flashing for a tight fit.
  5. Continue this process to install step flashing at every butt joint around the entire perimeter of your house.

This process gets more complicated where the roof meets your siding, as many rooves create complicated angles. But the good news is the installation process is relatively simple. Unlike siding flashing, which requires lifting the siding, roof flashing can be installed over your roof material.

The key for how to install roof flashing against siding is to use a step-down process. In this process, each of the flashing pieces sits partially on top of the one that is below it. This should create a ladder effect of sorts so that water must step down as it drips down your roofline.

Reliable Flashing and Siding Go Hand in Hand

At TruLog Siding, we know a thing or two about protecting your home from the elements. That’s because our metal siding is rated among the best at durability and longevity. When considering flashing your home, it’s also worth considering installing a siding material built to last. Get an estimate today.

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