How To Replace Basement Windows: A Step-by-Step Guide

Replacing basement windows involves careful measurement, proper removal of the existing window, leveling the new window in the opening, and sealing it securely.

Expect to pay between $100 and $700 per window, depending on the type and size. Compare this to the average cost of professional window installation — $200 to $1,000 per window, including labor.

You may need to replace old basement windows to deal with irreparable damage or to improve your home’s overall energy efficiency. If you’re finishing a basement, you may also need to replace windows to adhere to local building codes, which often require a working egress window for fire safety.

We’ll walk you through the supplies, safety considerations, and steps for basement window replacement. Our guide includes expert advice to help you decide whether DIY is the right route or if you’re better off hiring a pro to get the job done safely.

Supplies You Need To Replace Basement Windows

When replacing basement windows, wear eye protection, a dust mask, and sturdy work gloves to protect yourself from airborne dust and debris that you may kick up during the project.

You’ll need the following tools and materials to replace basement windows. Optional supplies in both lists apply to jobs in finished basements where drywall repairs may be necessary afterward.

Tools

• Eye protection
• Dust mask
• Work gloves
• Tape measure
• Hammer
• Pry bar
• Drywall saw (optional)
• Shop vac
• Hand leveler
• Power drill
• Caulk gun
• Utility knife
• Pencil
• Putty knife (optional)

Materials

• Replacement window
• Flashing tape
• Shims
• Screws
• Caulk
• Spray foam insulation for windows
• Drywall patch (optional)
• Joint compound (optional)
• Furring strips (optional)
• Joint tape (optional)
• Joint compound (optional)

6 Steps To Replace Basement Windows

The process for replacing a basement window is fairly straightforward but it can vary depending on the window material. Review the following steps carefully before deciding whether or not DIY is the right approach for your home improvement project.

1. Measure Accurately and Purchase Windows

Your replacement window needs to be slightly smaller than the existing rough opening. Take careful measurements of your window from the home’s exterior.

Get the width by measuring horizontally from the top, middle, and bottom of the window opening. Use the smallest of the three measurements and deduct ⅛ of an inch to account for the insulation you’ll apply later. Repeat this process for the height by measuring vertically from the left, middle, and right sides.

Next, measure the depth of the frame from the exterior siding to the interior frame. This will ensure that you choose the right window type, as different materials vary in thickness. Check all your measurements again to ensure accuracy, then purchase a right-sized standard or custom window to fit your rough opening.

2. Remove the Old Window

This step will vary based on the type of window you have. Vinyl windows are the simplest type to remove, and they are more common in newer homes. Aluminum window frames are more labor-intensive to remove.

Vinyl Window Removal

“A vinyl window is directly secured into the concrete and can be removed by leaving in the original nail fin and cutting the window out externally,” said Alex Vinet, a client services specialist for Custom Exteriors in Berthoud, Colorado.

Use a utility knife or saw to cut the window out and take care not to drop it when pushing it through the opening.

Aluminum Window Removal

“Most homes from prior to the mid-2000s have aluminum windows surrounded by a concrete foundation,” Vinet explained. “The level of difficulty will depend on how deeply embedded the old frame is in the concrete.”

Use a hammer and pry bar to remove any interior trim, taking care not to break the window glass. Unscrew or loosen the hinges that attach the window sash to the frame. Remove the glass insert and window screen. In a finished basement, this step may require cutting back drywall with a drywall saw to access the full window frame.

With these components out of the way, take the remaining window assembly out of the rough opening. If you’re removing an aluminum window embedded in concrete, cut the top of the window from the center with a Sawzall. Pull and pry the metal out of the concrete with a pry bar.

3. Prep the Opening for the New Window

Clean up the surface of the window frame. Cut away any leftover caulk with a utility knife and get rid of flaking paint with a hand scraper. Sand down any rough surfaces and use a shop vac to clean up any remaining dust and debris.

Finally, attach flashing tape up both sides of the opening to help prevent moisture issues and protect the wood frame.

4. Dry Fit the New Window

Slide the new window into the rough opening to ensure a proper fit. Use shims to get it snug and a hand leveler to get it level and plumb with the opening.

5. Secure and Seal the Window

With your window in place, apply a bead of caulk around the perimeter of the window from the exterior. Once the caulk sets, use a utility knife to cut away any excess. Then spray a window-grade expandable spray foam insulation to seal the gap between the window and the concrete foundation. Let it set overnight, then cut away the excess.

If you have any bare wood window parts, apply a coat of exterior-grade primer and two coats of exterior paint.

6. Make Any Necessary Repairs

If your window replacement involves cutting back drywall, make the necessary drywall repairs using the optional tools and supplies listed above.

How Much Does Basement Window Replacement Cost?

A replacement window costs DIYers between $100 and $700 for most basement openings, with costs varying mostly by window type and whether or not you need a custom window size.

Pro Vs. DIY

While most of the cost of professional basement window replacement is for the window itself, labor is also a factor. Hiring a pro costs $40 to $100 per hour on top of material costs. This means you can expect to pay $200 to $1,000 on average to have a pro install a single basement window.

Costs are sourced from contractor estimates used by Angi and HomeAdvisor.

It takes the average homeowner about six hours to complete a DIY basement window replacement, while it may only take a pro about an hour.

Signs You Need To Replace Your Basement Windows

Several signs can help you determine when a basement window needs to be replaced. Recognize these signs early and replace the window as soon as possible to mitigate more severe damage to your home’s foundation or interior:

• Condensation between glass panes
• Difficulty opening or closing the window
• Drafts coming from the window
• Visible damage or rot to the window or frame
• Water or moisture infiltration

If you have difficulty operating a window, it can mean that the home’s foundation has settled, the frame has warped, the hardware is worn out, or the window is simply too old.

Maintaining Your Basement Windows

After you’ve replaced a basement window, maximize its lifespan with proper maintenance, which should include:

• Checking for drafts in the winter
• Regular inspection of the window seals, frame, and glass for signs of damage or wear
• Routine cleaning with a mild detergent to prevent dirt buildup and allow light in

“Each manufacturer has their own maintenance requirements, which are typically given with their warranty information when the product is purchased,” Vinet said. “Thoroughly read the warranties. A lot of window manufacturers will not warrant a product that is not installed properly, or not installed by professional installers.”

Next Steps

Now that you know the process to remove and replace basement windows, you can evaluate your windows to determine whether a DIY project is possible.

“I would not suggest a homeowner do a DIY replacement on basement windows unless they are vinyl windows,” Vinet said. She also pointed out the importance of accurate measurements. “It sounds like a very simple task. However, this is an art and is best done by a seasoned professional to avoid unwanted mismeasures and costly mistakes. Orders are non-returnable if the measurements provided are not correct.”

Vinet recommends knowing the following before starting a DIY basement window replacement:

• Whether your municipality requires a permit
• Whether your windows are required to be tempered
• Egress requirements

If you’re removing a vinyl basement window and want to try your hand at DIY, contact a window supplier to get started. Otherwise, you’ll want to get quotes from at least three general contractors that specialize in windows, exteriors, or basement renovations.