What is Flashing a Window? It’s Not What You Think

Flashing a window… what is that? Let me tell what it isn’t. It’s not someone else going up to your window and exposing their body to you. Or vice versa.

Actually, window flashing is essential for protecting your window and home from water damage.

Window flashing is when you apply a water-repelling material around your window to protect the window and window frame from water penetration. It’s typically a system of different materials that all work together to do one thing: lead water away from your window and home.

Why Window Flashing is Important

Flashing a window may sound weird, but it’s very important for your home’s functioning. It’s a process that happens during your home’s construction, so you’ve probably never heard of it before.

Let’s imagine your house is a box with 4 walls and a roof, then water can’t get in at all. It’ll just slide down the roof and down your walls.

However, in a real house, there are windows. Windows are cut outs in your walls. They’re a possible way for water and the elements to enter your home because you now have holes in your walls.

Flashing makes sure that these “holes” don’t let in water, which can cause mold, mildew, rot, and other unwanted side effects.

Without flashing, your house will break down over time, especially if you live in a rainy or wet place such as the Northwest or near the Gulf Coast.

When is Window Flashing Installed?

Since window flashing is so important, how do you know if your windows have flashing.

Window flashing is supposed to be installed during the initial construction of your new home.

When you get your windows replaced, the window contractors typically use the flashing that’s already there. You can ask them if your home has window flashing installed. If not, then this is a great time to install it.

How is Window Flashing Installed?

There are different methods for window flashing. Some common materials are metal or plastic sheets, sealant tape, and water-resistant barriers.

Each home’s window is custom flashed to meet all of the standards to lead water away from the home.

In the video below, you’ll notice that he’s using a combination of custom cut and bent aluminum sheets that fits on top of his window to prevent water from sitting on top of the window.

For the area around the windows, you can apply water-resistant barriers to prevent water from entering your home.

Here’s a quick how-to on how a window is flashed:

Step 1: Installing Weather Resistive Barrier

The first step to installing window flashing is to make sure that you have a weather resistant barrier around your home. New home builders commonly use Tyvek. Just look for “house wrap” or “home wrap” at your local home improvement store.

Tyvek comes in large rolls. You then have to tape the Tyvek or house wrap to make sure it stays in place.

Step 3: Cut the Weather Resistive Barrier for Your Window

The video above shows someone properly cutting the Tyvek to create a hole for their window.

Use a utility knife to make an I-cut down the middle of the window opening. Then tape sealant tape to fasten each side’s flap around the inside of the home.

So now we have the WRB around the sides of the window opening. Next is the bottom of your window.

Step 3: Install the Sill Pan Flashing

The sill pan flashing is at the bottom of your window. It’s to make sure that water doesn’t sit between your window sill and window after a good rainful.

It’s sloped, so that the water will flow outward and down. Here is an example of a sloped sill pan desired for window flashing.

There are different options for this. In the video above with the Tyvek, he’s using an adhesive sill pan called Flexwrap. You’d need to cut out an extra foot for the flashing to extend six inches up on each side. Make sure that it’s flat and secure.

Step 4: Install Your Window

Now that your hole is partially flashed, it’s ready for the window unit to go in. Make sure you follow the proper instructions for your window replacement. It’s best to have a professional do all of this because no one wants water damage to their home.

If you’re doing this as a DIY project for one window, be sure to go through each step carefully. Make sure that there is no part where water and sit or enter your home.

Caulk the window on the top and the sides. It’s best not to caulk the bottom because you want water to escape from the bottom if it ever gets inside.

Step 5: Install Window Jamb Flashing

There’s so many weird window part names, aren’t there?

The window jambs are the sides. The head jamb is the top. The sill pan is the bottom.

In the video below, he’s using 4 inch flashing tapes. Start one inch above the nail flange and then make sure it’s flush all the way down. Make sure you have an extra six inches above and below on each side for enough overlap.

Step 6: Install the Head Jamb Flashing

Make sure that your flashing material is one foot longer than the window itself, so six inches can extend on each side.

Overlap is important to ensure there’s no holes that can let in any water.

Step 7: J-Rolling

Now that you have the majority of your flashing materials adhered to the areas surrounding your window, it’s time to roll it down.

Now you get a lot of pressure on all of your tapes. The friction also helps the adhesive stick more.

Step 8: 45 Degree Covers

At each top corner of your window, add about six inches of flashing material tiled at a 45 degree angle from the window.

J-roll it for maximum adhesion and pressure.

Here’s another video demonstrating all of the steps together on how exactly a window is flashed. This is a bit different from the video above because it uses a different system.

As we’ve discussed before, window flashing can be done using a variety of different materials and different methods as well.

The end result is that water is led away and out from your home.

Do Replacement Windows Need Flashing?

What about when you get your windows replaced? Do you need new flashing?

In an ideal world where money and time is limitless, you would get new flashing when you get new windows. But it’s not an ideal world.

Getting new flashing requires the contractor to remove your current siding around your window, remove the current flashing, and rebuild it. After that, they still have to get new siding. It’s expensive and it takes time.

Plus, not many people replace their windows and siding at the same time, although it’s recommended.

Advantages of Window Flashing

Now that we know what window flashing is, let’s look at all the advantages of having properly installed window flashing in your home.

Window Flashing Protects Your House

Water is unavoidable. You’ve got rain, snow, storms, and condensation. Water also causes a lot of unwanted damage to your home, including rot, mold, and mildew if left untreated.

Window flashing leads water away from your home. It leads the water away and out from your house. This way, you don’t get any water pooling up near your windows or flowing down your walls.

Finding a Professional for Window Flashing

Flashing a window is serious business. It’s not a job that should be done as a DIY project. If you don’t think the window flashing on your home was properly installed, contact a window flashing professional to make sure that your home doesn’t suffer from future water damage.

If you’re looking to build a new construction home, you now know that all of your windows need window flashing prior to placing the siding on top of it.

Contact a local contractor or multiple ones to get a variety of estimates and opinions on your home improvement project.

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