Skip to Content

Installing a Window in an Existing Wall

Sharing is caring!

Installing a window in an existing wall. These are some process photos for how to install a window in an existing wall.

This post may contain affiliate links which may earn me commissions should you click through them and take certain actions. As an affiliate for Amazon, Cricut, xTool, Home Depot, and other sites, I earn from qualifying purchases. Please DIY carefully. View my full legal disclosures here.

Please read the whole post so you don’t miss any important information!

This kids’ bathroom was really dark and small; the dark shower curtain also didn’t help make the room feel inviting. My kids refused to use the room to shower. And with the light switch on the opposite site, I can’t blame them. I know FOR A FACT that MY brother would have turned the light off on me, leaving me in the pitch dark. It was only a matter of time before one of the boys decided to mess with each other.

We decided to add a window and complete some other renovation projects to this outdated bathroom. The window was the first step.

This is the window “before” and after from outside of the house…

And inside the house before the trim was installed.

I LOVE how it came out… we did some further updates on the bathroom so make sure to check those out too!

How to Install a Window in an Existing Wall

We do a lot of DIY projects, but for this, we hired a contractor. The window was on the second story and we didn’t have a ladder tall enough to reach the area. We also weren’t very confident that we could do a good job. This seemed like a good one to hire out to a professional.

That said, I want to show you some photos of the process. Maybe someday we would be comfortable DIY’ing the addition of a window or door on the first story of the house or shed. It’s really interesting to see the progress, as well as to see the final results.

I also asked the contractor to do a non traditional frame around the window. I LOVE how it came out.

Here are the process photos of the bathroom from both the inside and the outside of the home. You can get an idea of how hard this task would be to DIY, depending on your comfort level. I feel like you should definitely plan to setup scaffolding and own a big ladder if you want to do installation on a 2nd story window.

Personally? This is a job I may tackle on our sheds first. If I mess up, it won’t be a crisis. I’d be hesitant to tackle this on our home. But when we were deciding if we should DIY or not, I wished for a more basic ‘how to’ tutorial to determine if this was DIY’able.

This is the “tutorial” I wish I had.


If you have plumbing or electric in the wall that you plan to demo, this will be much more expensive to do. It’s a good idea to drill a small hole in your wall and insert an endoscope to see what’s back there. You’ll likely need to work around insulation, at the very least.

When you’re choosing the size of your window, remember that the frame of the window will also take up space. If you can use the current studs for the window, your process for framing isn’t quite as complicated.

You’ll need a number of supplies, including 2x4s for framing out the window, the window (finding a window that matches your other windows is important), and drywall. You will need to use drywall mud, primer, and paint after your finished with the installation. You may need more insulation, as well.


Here are some pictures of the demo process. They started by demo’ing a bit from the inside, then worked from both the outside and inside to complete the job. Obviously this is a situation where they needed to be VERY careful not to demo more wall than necessary.

Photo of a hole in the siding, created by the contractor installing the window.

Scaffolding to help make the job easier and the ladders steadier (maybe?).

Fixing the Exterior of the Home Where The Window Will Be Installed

There’s a lot that goes into making sure that, when your window is placed, water (etc.) can’t leak into the house. I’ll add a video to the end of the blog post of how one vlogger did his so you can see more of that part of the process. There are trim pieces to match the siding, as well as waterproofing tape around the edges.

Window placed in the hole in the siding.
Exterior photo of the window after installation.


This is the best picture that I have of the framing. All walls have 2x4s or 2x6s as part of the frame. They provide the supportive structure of a home and drywall, insulation, siding, etc. are all added to keep your home cozy and to hide the ‘guts’ of the home.

Depending on the size of the window, you may need a different size frame, but the solid frame of 2x4s gives the installer something to attach the window to. Windows could not be attached to drywall or siding alone; they’d fall right out.

I believe he used two existing vertical 2x4s for this window, and simply added the horizontal pieces. When doing this work, it’s important to remember not to remove insulation (permanently). That helps reduce heating and cooling costs in your home.

Framing that will go around the window above a toilet. There's a hole where they started cutting away the siding of the house.

Placing and Securing the Window

Once the space is ready, the window can be placed and attached. There are panels inside windows that can be popped out so you can screw the window into a wall stud.

Window once the drywall was replaced and mudded over.

Replacing the Drywall and Using Drywall Mud

When the contractor installed the window, he tried to minimize how much demo he did on the wall. Ideally, you want to take off the smallest amount possible so that you can frame, install the window, and repair the drywall. It’s simply less work.

Due to the small size of the window, he didn’t need to remove the toilet for the project and he was able to do minimal drywall work.

I *believe* this was a picture of how they used drywall scraps to repair the walls after the window was installed.

The contractor used scrap drywall to repair the areas that were cut away to install the window.

This involves a couple of coats of the drywall mud and related dry times.

Drywall mud around the window.

We did not have him prime or paint the area after; this was something I tackled later on when we finished the rest of the project.

Caulking the Window

To prevent water and cold/hot air from coming into the house, the window needs to be caulked. This also keeps critters (like stink bugs!) from getting into the house.

Adding the Window Sill and Framing

As the last step (aside from cleanup), they added the window sill. Rather than go the traditional route, I opted for this somewhat square/blocky look that I saw on a Pinterest pin. The one challenge to this shape is that placing a curtain rod on the outside of the frame is impossible. Instead, I bought a small pressure rod for the inside of the window. I think you could opt for interior mounted blinds too.

Framing for the window. I LOVE this style.

The window addition was one of the most expensive parts of our bathroom renovation, but it made a HUGE difference. The natural lighting makes the room feel inviting. We replaced the bathtub, added a glass bathtub door, and used DIY white waterproof shower wall tiles to make the bathroom feel even more open and bright.

If you think this MIGHT be something you want to tackle, this is a better video showing the whole process by a professional.

Please share and pin this post! If you make this project, share it in our Stuff Mama Makes Facebook Group. We have regular giveaways for gift cards to craft stores. You can also tag me on Instagram @doityourselfdanielle; I love seeing everything you make!

Finished window added to a small bathroom to allow natural light into the room.

Sharing is caring!