Can You Enlarge A Basement Window? [And How To]

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A basement can serve as your storage room, activity area, or bedroom. Given the numerous purposes that basements serve, basement windows can be important for a number of reasons. Perhaps you want to let in more natural light, or maybe you want to provide a viable egress route from the basement. But is it actually possible to enlarge a basement window? We did the legwork to find the answer. 

You can enlarge the basement window despite its location being in between the foundation and structure of your home. With the right equipment and understanding of how construction works, you can increase its size to accommodate emergency use and home utility needs. The basic steps for the project are as follows:

  1. Gather all the required materials
  2. Prepare the basement window for restructuring
  3. Expand the window opening
  4. Install the new window

Calling an industry expert to conduct an assessment will give you a better idea of what's possible with your particular space. But if you still have some questions about the process, don't worry. In this post, we'll dig into the important information that will help you prepare and finish the work by yourself or with the help of an expert. Without further ado, let's get into it.

Empty room with white doors closet, sand beige walls, carpet floor in a basement. Can You Enlarge A Basement Window [And How To]

How To Enlarge A Basement Window

Expanding your tiny basement windows can be tough work to do by yourself, especially when you are not particularly skilled in this area of construction. That is why most homeowners hire professionals to do the work for them. 

Red and yellow tulips in a flowerbed near a house with a basement

But if you're up for it, you can enlarge the basement window by yourself by following these steps:

1. Gather All The Required Materials

First, check the building code specifications in your locality so you can confirm the allowable window size for your basement. 

Once you have dealt with the requirements, you are now ready to conduct the preliminary preparations for enlarging your basement window. We recommend that you prepare the equipment and tools below beforehand.

A simple materials checklist for a window enlargement project usually includes these items:

  • The new window that meets the local building specifications
  • Safety goggles
  • Face mask
  • Plastic to cover the window opening
  • Shims to fix the window in the opening
  • Industrial earplugs
  • Concrete saw
  • Sledgehammer
  • Shovel
  • Level
  • Wheelbarrow
  • Brick chisel
  • 2x4" piece of wood
  • Mortar
  • Deck screws
  • Caulk

2. Prepare The Basement Window For Restructuring

Using a shovel, dig out the ground around your window, ensuring you establish a 1-foot separation from each side of the window to the adjacent soil. The hole needs to have the height of the new window, with around 5 inches additional clearance from the ground. 

If you are doing everything by yourself, we recommend laying a tarp where you put all the ground to avoid making a mess. You can also dispose of the dirt immediately with a wheelbarrow as you dig through.

3. Expand The Window Opening

Mark the wall with a level line so you can avoid excessive demolition as you enlarge the window opening.  

Following the score or level line, use the concrete saw to cut the wall beneath the original window and sidewalls. Remember not to put too much force into cutting the concrete, and let the blade naturally make its way into the block.

If you are utilizing a dry concrete cutter, only run the saw for 30-40 seconds at a time to avoid overheating. 

Your foundation may be too thick for you to cut through the wall from only one side, so we recommend cutting halfway through each side of the wall.

After that, push or smash the concrete blocks out with a sledgehammer and clear the remaining debris. You are now ready to install the new wider window.

4. Install The New Window 

The window installation is the most time-consuming part of the process. To do so, follow these steps:

How To Install An Egress Window In A Concrete Basement Wall

1. Smooth the window opening with a brick chisel to remove the chips and rough edges. Stuff the open blocks with mortar. After which, cover them with plastic in preparation for the sill installation.

2. During the installation of the sill, drive deck screws halfway through the sill. The screws will provide a better foundation and integrity to the window when you push the sill to the slab of mortar.

3. Fix up the window frame to the opening, anchoring each side frame with screws for stabilization. Use exterior caulk to seal the spaces between the frame and concrete afterward.

4. You will now install the new window. Put shims on top of the sill and slowly install the window. Insert shims on each side of the window as you progress. The shims will allow you to have some room for adjustments later when necessary.

5. Check the window with a level to ensure it is not lopsided. Slowly cut the shims upon verifying that the window is well-fixed onto the opening. Drive screws or nails to better attach the window to the frame.

6. Pump caulk on the exterior and interior sides of the window to help seal hollow spaces between the frames and the wall. 

7. Lastly, create a beveled edge at the bottom of the window. To do so, place a 2x4" piece of wood 7 inches away from the window foundation to serve as the straightedge guide.

Then, fill the space to the brim with mortar mix. Wait at least 24 hours for the mortar to completely dry. And you are done with the basement window enlargement project.

How Big Can A Basement Window Be?

Brand new furnished modern house in Montreal's Beaconsfield

An egress window should have a net clear opening of 5.7 square feet at the very least. In other words, the window should be at least 20 inches wide and 24 inches high, just enough to accommodate and an adult man.

But these are just standards based on the provisions of the International Residential Code. The specifications may vary per locality because of factors that may affect the utility of egress windows. That is why you must first consult with your local officials about their particular guidelines.

It's worth noting, though, that all egress windows should open from the inside and that nothing should obstruct it from the outside for safety reasons.

What Is The Maximum Height A Window Can Be From The Floor In A Basement?

The maximum height of the egress window from the floor almost always remains constant among the differing egress window requirements in different localities.

International and local codes agree that an egress window should only have a maximum height of 44 inches or 3.7 feet off the floor. This height requirement starts from the base of the window or the sill, then measured down to the concrete floor.

If you want to know more about other basement height requirements, read through this post: What Is The Minimum Height For A Basement Ceiling?

How Much Does It Cost To Make A Basement Window Larger?

The expenses for enlarging a basement window do not vary significantly from what you paid for the original window installation. The project will cost $3,901 on average.

However, these expenses are fluid and can range from $2,549 to $5,299 depending on the size of the window, the labor associated with window removal, ground excavation, wall demolition, and the number of windows you choose to install.

If you plan to pay a professional to do the work, you need to know how much to allocate for each service. Here is the cost breakdown:

  • Ground excavation for the window and drainage: $300 – $500
  • Cutting and clearing of the window opening: $350 – $800 (will vary based on opening size)
  • Window frame preparation and installation: $150 – $300 (will also differ based on opening size)
  • Egress window, depending on the material, glass quality, dimensions, styles, etc.: $100 – $1,000+

How Many Egress Windows Do You Need In A Basement?

The International Residential Code states that all basements should have at least one egress window that meets the size requirements. 

However, a 200-square foot basement used as a living space, activity area, living room, or bedroom requires a secondary egress window. This second window should follow the size specifications used for the opening, window sill, and the maximum height of the window off the floor. 

bright basement window with staircase. Can You Enlarge A Basement Window [And How To]

In Closing

You can expand small basement windows to meet the minimum requirements the International Residential Code provides for your safety if an unfortunate event happens. The information and steps provided in this blog will help you start.

You might be wondering whether or not you can build a basement under an existing house. Read this post to find out: Can You Build A Basement Under An Existing House?

Best of luck!

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