Basement Window Replacement: Steps, Styles, and Egress Rules

A cracked, rotting, or drafty basement window drags down your comfort and your heating bill at the same time. The upside is that swapping one out is a weekend job most handy homeowners can handle with basic tools.

This guide covers how to replace a basement window start to finish: picking the right style, measuring the opening, and setting a new unit into a steel or wood frame. It also walks through the egress code rules that kick in when the window doubles as an emergency exit.

Basement Window Replacement Costs

What you pay comes down to the opening size, the window style, and whether you hire out the labor. Doing it yourself saves the install cost, while a pro adds a watertight, code-correct fit. Most standard basement windows run about $400 to $1,000 replaced. A full egress conversion is the outlier at roughly $2,500 to $5,000 installed, since it means cutting the foundation and building a window well. Here is a breakdown of the typical costs for window replacements:

Types of Basement Windows

Basement windows prioritize function over fashion, but you still have choices. The right style depends on how much ventilation, light, and security you need.

Hopper Windows

Hopper windows are the go-to choice for many homeowners. They are hinged at the bottom and open inward, making them excellent for ventilation. Because the sash tilts in, they are easy to clean and often feature a tight seal against drafts when locked.

Awning Windows

Awning windows are similar to hoppers, but they hinge at the top and open outward. This design creates a small “roof” over the opening, allowing you to keep the window open for fresh air even when it is raining lightly.

Sliding Windows

Sliding windows (or gliders) move horizontally on a track. They are simple to operate and do not protrude into the room or out into a window well. However, they typically only open halfway, which limits total airflow compared to a hopper.

Glass Block Windows

Glass block windows are constructed from thick, brick-like glass cemented in place. They are arguably the most secure option and offer great privacy, but they do not open. These are ideal for areas where ventilation isn’t a priority but security is.

Egress Windows

An egress window is large enough for an adult to climb out during an emergency, and building codes require one in any basement used as a sleeping room. The catch is that the opening has to hit specific numbers, not just look big enough.

Under the International Residential Code (R310), the window needs a net clear opening of at least 5.7 square feet (5 square feet for a ground-floor opening), a minimum opening height of 24 inches, a minimum width of 20 inches, and a sill no higher than 44 inches above the finished floor (IRC R310). All four have to be met at once, measured with the sash fully open.

Hitting those numbers in a basement usually means cutting the concrete foundation to enlarge the opening and adding a window well. The well has its own minimums: at least 9 square feet of floor area with a 36-inch projection from the wall, plus a permanently affixed ladder or steps if it is deeper than 44 inches.

How to Measure for a New Window

You cannot install what doesn’t fit. Learning how to measure correctly is the most critical step of the project.

If you are removing the entire frame (down to the concrete), you need to measure the “rough opening.” Take three measurements for width (top, middle, bottom) and three for height (left, center, right).

Always use the smallest dimension as your final measurement. If you are just replacing the glass or the sash inserts, measure from the inside of the jamb.

How to Replace Basement Windows With Steel Casing

Steel “buck” frames are common in older homes. They are durable but prone to rust and offer poor thermal insulation. Replacing them with a modern vinyl unit will significantly improve energy efficiency.

Here is the gear you need to get the job done:

What You Will Need

• Cold chisel.
• Mallet or mini-sledgehammer.
• Reciprocating saw with metal blade.
• Pry bar.
• Replacement window.
• Siloxane concrete sealer.
• Putty knife.
• Miter saw.
• PVC or wood trim.
• Construction adhesive (Liquid Nails).
• Drill/driver.
• Tapcon concrete screws (double-threaded).
• Hammer drill.
• Exterior filler or silicone caulk.
• Shop Vacuum.
• Safety glasses.
• Face mask.
• Earplugs.

1. Remove the Old Metal Frame

Locate the screws or clips holding the steel frame to the concrete. If they are rusted shut, use your drill to bore them out or a reciprocating saw to cut them. Use a pry bar to leverage the frame out of the foundation. If it is stubborn, you may need to cut the frame into sections.

2. Clean and Prep the Opening

Vacuum up the dust, crumbled concrete, and rust flakes. Inspect the concrete rough opening for high spots or ridges that could interfere with the new window.

Chip away obstructions with your hammer and chisel. Once the surface is clean, apply a Siloxane Concrete Sealer to the exposed concrete to prevent future moisture absorption. Let it dry completely.

3. Install the New Window

Remove the sash and screen from your new window frame to prevent damage and make the frame lighter to handle. Center the frame in the opening and use shims to ensure it is level and plumb.

Using a hammer drill, pre-drill holes into the concrete through the frame’s pre-made holes. Drive the concrete screws in carefully; do not overtighten, or you might warp the vinyl frame.

4. Seal the Gaps

Apply a generous bead of exterior-grade silicone caulk or low-expansion spray foam between the window frame and the concrete wall. This seal is your primary defense against water and bugs. Smooth the caulk with a putty knife for a clean look.

5. Reassemble the Window

Snap the sash and screen back into the frame. Test the operation to ensure it opens, closes, and locks smoothly.

6. Apply Interior Trim

For a polished look, measure and cut trim to frame the window interior. Secure the trim with construction adhesive. This covers the gap between the window and the drywall or concrete, hiding any shims or foam.

Replacing a Basement Window With a Wood Frame

Wood frames are easier to remove than steel, but they are often rotted or water-damaged. The removal process is slightly different, but the installation principles remain the same.

Here is your checklist for wood frame replacement:

What You Will Need

• Hammer and pry bar.
• Reciprocating saw.
• Spirit level.
• Drill/driver.
• Utility knife.
• Mortar mix (if repairing concrete).
• Composite shims.
• Low-expansion window foam.
• Concrete screws.
• Exterior caulk.
• Trim.
• Construction adhesive.
• Shop vacuum.

1. Remove the Old Unit

Take out the window sash first. Use a reciprocating saw to cut through the nails or screws fastening the wooden jamb to the framing or concrete. Use a pry bar to pull the old wood frame out of the opening.

2. Clean and Repair the Opening

Vacuum the opening thoroughly. If the removal process chipped the concrete foundation, use a small amount of mortar to repair the divots. Ensure the sill (bottom) is flat and level. Apply a concrete sealer to waterproof the rough opening.

3. Install the New Window

Dry fit the window to ensure it fits. Apply a bead of caulk to the concrete sill before setting the window in place. Center the unit and place shims under the corners to level it.

Drill pilot holes through the frame and into the concrete or wood buck. Secure the window with screws, checking frequently with a level to ensure it hasn’t shifted.

4. Insulate and Seal

Fill the gaps around the perimeter with low-expansion spray foam.

5. Finish the Exterior and Interior

Once the foam cures, trim the excess with a utility knife. Apply a final bead of silicone caulk on the exterior where the window meets the concrete. Install your interior trim to cover the gap for a professional finish.

How to Replace Basement Window Glass

If your frame is solid but a baseball went through the glass, you don’t need a full replacement. Fixing a cracked pane is a cost-effective repair.

Gather these tools before starting:

What You Will Need

• Heavy-duty gloves and goggles.
• Hammer.
• Putty knife.
• Duct tape.
• Heat gun.
• Replacement glass pane.
• Glazing points.
• Glazing compound (putty).
• Linseed oil.
• Paintbrush.

1. Remove Broken Glass

Safety is paramount here. Wear thick gloves. If the glass is shattered but still in the frame, tape over it with duct tape to hold the shards together while you pull them out. Wiggle the pieces gently to remove them.

2. Clear the Old Putty

Old glazing putty is often rock hard. Use a heat gun to soften it, then scrape it away with a putty knife or chisel. You also need to pull out the old metal glazing points (small triangular clips).

3. Prep the Frame

Clean the rabbet (the groove where the glass sits) with a wire brush. Wipe it down with a rag damp with linseed oil; this conditions the wood and prevents it from sucking the oil out of the new putty too quickly.

4. Apply a Bed of Putty

Knead a small amount of glazing compound until it is soft. Press a thin layer into the primed rabbet grooves to create a cushion for the new glass.

5. Install the Glass

Press the new glass pane firmly against the putty bed. Insert new glazing points every 6 inches to mechanically hold the glass in place. Push them into the wood using the flat edge of your putty knife.

6. Glaze the Window

Roll the remaining putty into long “ropes.” Press these into the edge where the glass meets the frame. Hold your putty knife at an angle and smooth the putty into a neat, triangular bevel. Clean up any excess from the glass.

7. Paint

Wait for the putty to “skin over” (this can take days or weeks depending on the brand). Once dry, paint the putty and the frame to seal it against the weather.

FAQs

Easier Than It Looks

Replacing a basement window looks intimidating, but with careful measuring and the right seals it is a solid weekend project. Trading rusty, drafty frames for a tight new unit trims your energy bills and makes the whole basement feel less like a cave.

Grab your tape measure, confirm your numbers twice, and get to work. You will notice the difference every time you head downstairs.