​​Taking a shot at building an exterior shed or home extension?

Trying your hand at carpentry and construction can be a rewarding experience. The skills learned in both practices have wide-ranging applications, and you’ll learn a host of tricks and quick fixes for a myriad of different problems you may encounter around the home.

However, making and raising walls is one thing, but uncovering how to frame and install that wall with a window is quite another. While it may look simple to the outside onlooker, framing a window takes precise measurements, hard work, and a whole lot of patience.

Whether you’re getting to work at installing a window from scratch or reframing a window with a newer style, we’ve got everything you need to know about how to frame a window. We’ll cover tips and tricks for getting installation just right, as well as what you need to keep in mind before making the call and purchasing the materials.

What You’ll Need

Drill bits and a meter on the floor

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No construction job is complete without a list of materials to purchase, and when it comes to window framing, you’re going to need a whole lot more than the window itself.

This is also going to depend on whether or not you need to install a rough opening first. For those unaware, a rough opening, or RO, is a term used to describe the hole contractors leave in a wall for the future installation of a window. An RO looks to be little more than a hole in a wall’s framing, but we’ll get into how to install an RO a little be later on.

For now, we’ll work from the assumption that you’ve already got your RO and just need the materials for the window installation. In which case, you will need:

  • A crowbar
  • Levels
  • Ladders
  • Caulk
  • Replacement wood (if applicable)
  • Trim (if applicable)

These are the basic tenants of a window reframing job, but depending upon what you’re doing and where the window itself is, you may need different types of these materials.

For example, if you’re working with a second story window or higher, getting a ladder is going to be crucial—even if you’re going to be working from the inside. Access to both sides of the window is crucial for ensuring that your window framing is rock solid.

At the same time, if you’re replacing a particularly old window, you may need more replacement wood than if you’re simply installing and framing a window from an existing and new RO. Keeping some 2x4s or 2x2s handy will aid in this process.

We recommend you take the time to remove the old window and assess the framing of the RO to see if any pieces have been rotted away or otherwise are compromised. This determination will help ensure you’ve got everything you need and won’t have to stop your framing for an unexpected trip to the hardware store.

But assuming you’ve got your supplies in order and you’re ready to work, let’s take a look at getting your RO in order and framing your window.

The Rough Opening Installation ​​​​​


If you’re raising the walls of a new structure yourself, you’ll need to make sure you build your RO to code and without compromising the structure of the surrounding wall.

tools hammer nails drill nut

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Most carpenters agree that setting up and installing your RO is going to require the following components:

  • Headers
  • A king stud
  • Trimmers
  • Cripples

To start, measure out the length of your header (which will connect two of the support beams on either side the wall frame) and install at the top of the wall. Nail in king studs to the header and the top plate to ensure everything is secured. They’re called king studs for a reason—so ensure your handiwork is on point here.

Trimmers then need to be nailed in, running down either side of the header against the side support structure. These trimmers need to run the length of the window, which will start at the bottom of the header and run down to the sill.

The window sill goes on next, connecting the two trimmers at their bottom end. And while the term is somewhat problematic, you’ll need to next nail in the cripples beneath the sill, connecting the bottom of the sill to the bottom plate.

Provided you’ve ensured the structure surrounding your RO is sound; you should be good to continue with your installation. Always remember to measure twice and cut once—to ensure that your hard work isn’t thwarted by a misplaced number or cutting the wrong piece.

Now that your RO is in place, it’s time to skip ahead to the finished wall and talk about how to frame a window. 

Reinstalling & Replacing Old Windows


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Our framing and reinstallation guide here assumes you’ve taken the time to get an RO installed in a new or existing wall. If you’re adding a window to an existing wall, we always recommend getting a contractor or stonemason out to professionally cut out the hole and get your home ready for the window. Provided you’ve completed the steps, here’s how to frame:

Remove any old trim from a pre-existing window in the correct spot and pry it out with a crowbar. Then take the time to measure the hole and remove any wood that may not be up to code.

You’ll want to install the new interior framing, trimmers, and sill to ensure that you’ve got a little under an inch of wiggle room on each side in comparison to the size of your window. The last thing you need is a window that’s too snug of a fit for the frame you’ve built.

Want to reframe a window and try to reduce energy costs and waste? You may also want to consider using a glaze on the wood you’ve used to build your window’s frame. Different types of window framing materials, such as composite frames or fiberglass frames, are also going to be more insulating of the outside world and may be worth considering.

Fiberglass especially is a great insulating material, and if you’re reframing your window to replace older components, why not consider replacing the components that may be forcing you out of a lower energy bill?

Regardless, once you’ve installed the new components, it’s fine to pick up the window and get to installation. Using caulk, seal the new window into the window sill and be sure to form a tight seal around all corners and edges.

Finally, if you’re working with a completed wall, you’ll need to bust out the trim and line everything up. Assuming you’re working with interior drywall, be sure to pick up trim ahead of time that’s large enough to bridge the gap between the window and drywall, but not too large as to undermine the size of the window itself.

Some types of trim are going to require the installation of many auxiliary parts, including a new windowsill atop the existing one. Just be sure to follow the instructions and always focus on proper sealing. Improper seals are common with DIY jobs such as these, so avoid any calls to carpenters by focusing on sealant that’s built to last.

Final Thoughts

No matter how you approach how to frame a window in your home, we hope that we’ve given you a few simple home hacks to get your home or shed looking beautiful again. But before you get to work, we have a few more things we’d like to go over:

First of all, building an FO from scratch is going to take a considerable amount of work. Due to the number of boards and precise measurements involved, we recommend getting a friend or family member to help out with the building process. There’s nothing like a second pair of eyes to help you make sure that your measurements are precise and adequate.

Likewise, when you’re installing the window itself, having a second pair of hands is going to be useful to ensure that you’ve lined up the window properly and aren’t spreading the caulk too thin before pressing the window into it. As we’ve mentioned a proper seal is paramount to proper insulation, so make sure you’ve cut your boards as precisely as possible and installed correctly.

Otherwise, we hope that you’ve got everything you need to get started as soon as the materials come in. Framing and construction work may seem daunting at first, but when you know the terminology, and precisely how to best approach the problem, you may be surprised to find that your dream window is just a weekend away from completion.

And the best part? You can take pride in knowing that you earned the view from your window yourself.

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