How to Add a Window to a Basement (9 Steps)

Looking to create a basement playroom for the kids? Need an additional bedroom? Or, maybe you are looking to add value to your house by making the basement more attractive. Basement renovation possibilities are endless.

How do you add a window to a basement? The new, planned use of your basement will dictate what kind of window you’ll use.  Here are 9 steps to add a window in your basement:

• Check City Hall
• Gather tools and materials and protective equipment
• Ordering the right window
• Prepare the site
• Create a window well
• Cut the concrete
• Prepare for the window frame
• Frame the new window opening
• Install the window

If you are planning to add a bedroom in your basement, you’ll need to have a window – an egress window. But perhaps you want some natural light to find its way into the room. A new window is a perfect way to accomplish this. Here’s how to get it done in 9 easy steps.

How to Add a Window to a Basement

If your basement wasn’t built with an egress window (a window that can be used as an emergency exit), you may find yourself needing to add one. Many homeowners will call in a contractor to get the job done – and can plan to spend $1,000 and up on the project. With the right tools and the wherewithal, you can get it done for half the price. 

1. Check City Hall

The first thing you should do before adding a basement window is head down to city hall and find out if you need a permit or not. Adding a basement window is a change to the house’s permanent structure and many times such a change needs a permit. 

There are important factors to where you put it, like how close it is to a corner or another window, and most cities want to make sure you are putting it in the right place.

Other towns or cities have neighborhood ordinances that regulate the type of changes you can make on your house, especially if it is a visible change. Take the time to find out if they exist in your neighborhood and if it will affect where you plan on putting your new basement window. You don’t want to start cutting cement only to find out that you aren’t allowed to place it there.

2. Gather Tools, Materials and Protective Gear

You are going to need a lot of tools and materials to put in a basement window. It is not an easy job. Here are some of the supplies you will most likely need:

Tools

• Brick Chisel: This will be used to chip away concrete so you can have smooth surfaces.
• Caulk gun: You are going to need to seal the frame of the window.
• Saws:
  • Circular saw: You will need to make a window frame. This saw will help you cut wood for the frame. 
  • Concrete saw: You are going to need a saw to cut into your foundation. You can rent one of these at almost any tool store.
  • Diamond saw blade: This is for the concrete saw. You can rent it with the saw. You want it to be either 12” or 14”.
• Finish trowel: You are going to have to apply concrete to the edges of the window.
• Hammer: There will be nails to drive.
• Hammer drill: It will help when you get ready to cut the cement.
• Level: To ensure your window frame is level.
• Masonry bits: These are for the hammer drill when you drill starting holes into the foundation. Make sure that they are long enough to go through your basement wall.
• Maul: To help with any demo and to help remove the block of cement you will be removing.
• Tape measure: You can’t build or cut anything without it.
• Water sprayer: This will be needed when using the concrete saw on the foundation to keep the saw blade cool enough to continue.

Materials Required

• Galvanized screws: Needed for the window frame.
• Pressure-treated lumber – 2x10x10ft.: Needed to make the window frame.
• Lumber – 2x4x10 ft.: Needed for the window frame.
• Deck screws: Needed for the window frame.
• Concrete screws – 3/16 x 3 1/4-in.: To attach the window frame to the foundation.
• Plastic tarps: To prevent the concrete dust from getting in everything in your house.
• Concrete mix: To fill in any gaps when the window is in.
• Egress window/Small basement window: The most important material for the job.
• Exterior caulk: To seal the window.
• Shims: Needed to put the window in the frame.

Protection Equipment

• Hearing protection: The cement saw and hammer drill are extremely loud. You need protection for your ears.
• Dust mask: There is going to be a lot of dust and debris flying through the air when you start cutting the foundation. Wear a dust mask to prevent you from ingesting it.
• Safety glasses: Always a must when doing construction, but particularly important with all the dust and debris that will be flying around.

3. Ordering the Right Window

This may sound silly, but the most important material you are going to need is the window. Make sure to order the right size or you may find yourself in a mess you won’t be able to fix.

There are many basement window choices. Which window you go with will depend on why you are adding the basement window in the first place. Here are some of the most common basement window choices…

• Casement windows: these windows are hinged on the side and crank open either inward or outward. If you are adding a bedroom, casement windows are excellent egress windows because of the size of its opening. They are the smallest window that fits requirements for egress windows.
• Hopper window: hopper windows are the same style as casement windows, except they are hinged at the bottom of the window. 
• Awning window: these are also the same style as casement windows except they are hinged at the top. Awning windows do not make good egress windows because they do not open enough to satisfy most egress laws.
• Double-hung: this is the style that is most common in the rest of the house. They have two sliding pieces placed on top of the other, known as sashes, that slide over each other. These are not effective egress windows because they would have to be 5 ft tall to meet the minimum openable area requirements.
• Sliding window: these function similar to the double-hung, except the sashes are side by side. This is also a popular choice for egress windows. They do not have to be as tall as double-hung windows, although they do have to be 48” by 48” to meet requirements.
• Glass block windows: these are more stylish than functional. They cannot be opened. They do let in excellent light and many people like to have them put in because you cannot see into them, adding a level of privacy or security.

Egress Windows

An egress window can be thought of as an emergency exit.  According to the International Building Code, Section 1030 “Emergency Escape and Rescue”:

 “Basements and sleeping rooms below the fourth story shall have at least one exterior emergency escape and rescue opening. . . . Such opening shall open directly into a public street, alley, yard, or court.” 

So, if  you need an egress window, these are the requirements you’ll have to meet: 

The minimum net clear opening	5.7 sq. ft. This is the amount of free and clear space – large enough for first responders to crawl through the window will all of their necessary gear
The opening height	must be greater than 24”
The opening width	must be greater than 20”.
The bottom of the open window	must be no less than 44 in. off the floor.
No bars, grills or grates	The window must be able to be opened without any tool or key. Again, necessary for the safety of inhabitants and first responders.

While it is important to be aware of these regulations, you do not need to memorize or measure anything. Window manufacturers are well aware and will let you know if a window meets egress requirements or not.

4. Preparing The Site

Before you jump into cutting concrete, you are going to need to prepare the worksite. There are a few things that you need to take care of before you can start work on the foundation, both for your safety and to make sure things are done correctly. Before you put shovel to dirt you should…

• Call your utility companies and have them mark any pipes or wires that may be running by where you will be working. Not only will this protect you from gravely hurting yourself and others around you, but it is also the law. You must let utilities know when you are going to start any large digging project.
• If you are going to be putting in an egress window, you should stake out the area you are going to be digging out.
• Use masking tape on the basement wall and a chalk line to mark where the window will go so you have a good idea of where to cut and how the placement will look.
• Hang the 6-mil plastic from the basement ceiling, making three walls. This will keep the cement dust when cutting in one area and not all over your house. 

5. Creating a Window Well

If you are putting in a normal basement window, you can skip to step 5, but if you are putting in an egress window you are going to need to dig out and build a window well. Unfortunately, there are as many regulations about window wells as there are about egress windows themselves.

Window wells must:

• Be big enough that the well window can be fully opened.
• Have a “floor area” of 9 sq. ft. with a minimum dimension of 36” in both length and width.
• Have a permanent ladder or steps for climbing out of the window well if the well is more than 44” deep. The ladder must be 12” wide or more and stick out of the well at least 3”. It can’t be blocked by the open window or effect the required window well dimensions by more than 6”.
• Beneath a deck or porch, you need 36” or more between the window well top and the bottom of the deck floor joists. Many officials will tell you they need 60”

As complicated as this all sounds, there are many basic ways to create a window well that fits all these regulations. None of them are going to be easy, but all of them will allow you to build a safe bedroom or family room in your basement. Here are a few ways you can put in the required window well for your egress window…

• Concrete Walls: These are strong walls that will last forever. You can even use decorative brick to add flare to your well. If you are going to put in a concrete well, you need to…

1. Dig the well: you are probably going to need big-time equipment to get this done. You could try to do it with a shovel, but that would be extremely labor-intensive. Rent a backhoe and you will save yourself time and work. Make the hole 4” deeper and 8” wider than required by your dimensions.
2. Pack gravel: pour and pack 4” of gravel on the well floor.
3. Frame the well: use 2×4 to frame the sides, two coming off the wall of the basement, and one running parallel.
4. Well floor: pour concrete to fill the area between the planks you placed. Level out with a trowel. To ensure a straight, flat, layer, use a level. Cover the area with plastic and let dry for at least three days
5. Concrete forms: build concrete forms for each wall of the well. Place them where they belong.
6. Pour concrete: pour concrete into the space between the boards that make up your forms. Use a trowel to flatten the concrete on top of the forms and remove any excess. Put plastic sheeting over the forms and let the concrete dry for at least three days.
7. Take forms apart: use a hammer to take the forms apart.

If your walls are more than 44” tall, you are going to have to install a permanent ladder as well.

• Terraced Well: This is a popular choice because it eliminates the need to worry about many of the window well requirements such as the bottom of the well-being at least 3’x3’, providing a permanent ladder if the wall is over 44” high, and the well can’t interfere with the window opening. If you are going to put in a terraced well, you need to…

1. Dig out the terrace: dig each shelf 17” deep and 12” wide. Dig the bottom level at least 12” deeper than where you want the window bottom to be. On the base furthest from the wall, dig a 12” wide 6” deep trench for draining.
2. Pack with gravel: fill the bottom level with gravel until it is 6” from the window bottom. Pack the gravel with a 2×4 as you go.
3. Set the first row: cut 4×6 timbers to the desired length and place them perfectly level on the gravel base. Place the timbers together and backfill with gravel.
4. Set remaining levels: use a framing square to establish the setback from the previous wall and place the next set of timber. Backfill with gravel and move on to the next level.
5. Anchor the walls: using a hammer drill and masonry bits, predrill holes in the foundation. Apply caulk to concrete screws and drive them into concrete to secure timbers.

• Manufactured Well: If you are looking to save a little time and labor, you can always buy an already built window well. There are all types of materials and styles out on the market that you can just buy and install. If you are going to put in a manufactured well, you need to…

1. Pick out and purchase a well: make sure it comes with a ladder if local codes say it is needed.
2. Dig the hole: again, you are going to want to get a backhoe to do the work for you.
3. Prepare: the well should be installed so it sits 2 to 3 inches above ground level and 3 to 10 inches below the windowsill. Mark the top of the well on the wall. Spread a 12” layer of gravel in the hole. Extend the 12” layer of gravel 12” beyond the exterior dimensions on all sides of the well being installed.
4. Set the well:  center the well over the window and make sure it is level. Be careful the window well is set carefully and not bent or twisted during installation or the well cover may not fit properly. 
5. Don’t fasten before checking: check the well’s inside dimension before you fasten it to the wall. Once you are sure the well is properly set, drill mounting holes through the flanges on the well flange. Fasten the well to the foundation wall. Add about 3” of additional gravel  in the bottom of the well by the foundation wall
6. Backfill the well: you’ll need pea gravel or other small, draining stones, and fill the hole up to within about 12” of the top of the window well. Check out this video. At around 1:47, you’ll see how they backfill the well.

6. Cutting Concrete

Cutting a window hole in the foundation of your house is the most difficult step in the process of adding a new window to your basement. Your basement wall will either be concrete block or poured concrete. If it is poured concrete, you should probably call a professional to do the job for you and skip to step 5. The weight of the slab that you will be cutting out is going to be extremely heavy, so it is best to leave it for experts with the equipment to properly handle. At the very least, you should never cut your foundation without a few friends to help.

If you have a concrete block wall and are willing to tackle the job yourself here is how…

1. Put on your gear: there are many dangerous elements to drilling and cutting concrete. Make sure you have eye protection, ear protection, and a mask on while completing these steps.
2. Drill pilot holes: use your hammer drill and masonry drill bits and drill a number of holes completely through your basement wall. Drill your first hole in the center of the bottom line of your cutting area. Next drill holes in each of the four corners of the cutting area. Finally, you should put a hole in the center of the top cutting line and each of the two sides.
3. Mark outside cutting lines: you are going to have to cut on both the inside and outside, so use the pilot holes to measure and mark your cut lines on the outside wall. You should use your level and framing square to make sure all the lines are straight.
4. Cut the inside wall: next, cut a ½” deep grove along your cut lines with the concrete saw and diamond blade. Have a partner wet the blade as it cuts to reduce heat and dust build-up.
5. Finish with outside cuts: move outside next and complete your cuts from outside.
6. Knock out block: break out the block with a 4-lb. Hammer, starting at the top center, because it isn’t going to fall out on its own. Work carefully around the edges. For stubborn blocks, first, break out the core in the middle of the block, then break the block. And be careful, pieces of brick are going to fly.

7. Preparing For Window Frame

Once you have the block out, you are going to have to do a little prep work before you are ready to put the window frame in. You are going to find that the edges of your new hole are not smooth. Grab your brick chisel and maul and start chipping the sides of the opening smooth. 

Next, you want to fill in the open block cores that will be under the sill. To do this stuff newspaper or something similar in the open holes and then cement over the holes. Then cover the wet cement with plastic sheeting so water from the concrete won’t warp the sill.

Drive 3” deck screws into a treated wood sill and push them into the wet cement. This will anchor the sill and prevent the window frame from moving.

8. Frame The New Window Opening

Now that you have an opening in your foundation with smooth sides and an anchor sill in place, it is time to frame the opening for your new window. Here are the best steps for getting the frame in place.

1. Header: Start by building a header and hoisting into place at the top of the opening. Once it is in place, screw it into the floor joist above it.
2. Sides: Cut the pressure-treated 2×10 to fit the depth of the wall, then cut them to length for the sides of the frame so they are a tight fit. Using a scrap piece of wood and your hammer, bang each side into place so it is supporting the header.
3. Make plumb: Make sure the sides are plumb with a level. Once you are certain that they are perfectly vertical, toe screw them into the sill and header.
4. Anchor the sides: Get out your drill and mason bits and predrill holes through the frame sides into the concrete wall. You should countersink with a ⅜” bit. Use 3/16 x 3-¼” concrete screws to anchor the sides of the frame to the wall. Use shims to keep the frame straight and plumb while you are tightening the screws.
5. Caulk: Seal gaps between the wood frame and the concrete wall with any type of exterior caulk. If the gaps are more than ¼” wide, put a foam backer rod into the gap before you caulk.

9. Install The Window

Now that everything is in place, it is time to put the window in. Putting the window into the frame will go quickly compared with all the needed prep work. Most manufactures include installation instructions with every window, so if you read through them you should be fine, but here are the general steps…

• Center the window and level it with cedar shims. If you have someone to help, which you should, one person should hold the window as the other shims it. It is okay to temporarily tack the shim to the frame.
• Apply caulk around the treated wood frame behind the window’s nail fin. This will create a strong weather-tight seal.
• With the window centered in place, drive nails or screws through the nail fin into the frame. Be sure to check the manufacturer’s directions on whether to use nails or screws.