Replacing Broken Glass in a Single-Hung Window: Step-by-Step

Dealing with cracked, broken, or foggy window glass? Yes, you can often replace the glass in a single-hung window yourself, especially if it’s a simple single pane. It requires careful work and attention to safety, but it can save you money.

This guide provides step-by-step instructions for safely removing the old damaged glass and installing a new pane in your single-hung window sash.

Safety First! Working with glass is hazardous. Always wear heavy-duty work gloves and safety glasses throughout this process.

Need a refresher? Learn ce qu'est une fenêtre à guillotine simple – typically, only the bottom sash moves.

When to Replace Window Glass

Common reasons include:

• Impact Breaks: Rocks, balls, birds, etc.
• Stress Cracks: From temperature changes or frame settling.
• Failed Seals (Foggy Glass): Moisture between panes in double-pane windows.
• Scratches or Etching: Severe surface damage impairing the view.

Single-Pane vs. Double-Pane: What Can You DIY?

• Verre à simple vitrage : (One layer of glass) This is generally the most feasible type for DIY replacement. The process involves removing putty/stops, replacing the glass, and re-sealing.
• Double-Pane Glass (Insulated Glass Unit – IGU): (Two layers sealed with gas/air between) Replacing just one broken pane is not typically possible for DIY. If the seal fails (foggy) or glass breaks, the entire sealed IGU unit usually needs replacement. Alors que possible to DIY install a new IGU unit into the sash, it’s more complex and often best left to professionals or requires ordering a specific replacement unit. This guide focuses primarily on single-pane replacement.

Tools and Materials Needed

Gather these items before starting:

Outils:

• Safety Glasses (Essential)
• Heavy-Duty Work Gloves (Cut-resistant recommended – Essential)
• Putty knife (stiff and flexible)
• Flathead screwdriver
• Pliers
• Mètre à ruban
• Couteau utilitaire
• Heat gun (optional, helps soften old putty)
• Chisel or razor scraper (for cleaning frame)
• Caulking gun (if needed)
• Possibly: Small pry bar, rubber mallet

Matériels:

• Replacement Glass: Cut to size (see Step 4).
• Glazing Compound: (For wood frames) OR Exterior Glazing Tape/Silicone Sealant (For vinyl/metal frames).
• Glazing Points: (For wood frames).
• Painter’s Tape or Duct Tape: To secure cracked glass during removal.
• Optional: Sandpaper, wood sealer/primer (for wood frames), new vinyl glazing beads (if originals break), rubbing alcohol (for cleaning metal/vinyl).

Step 1: Safety and Preparation

1. Portez un équipement de sécurité : Put on your safety glasses and heavy gloves avant touching the window.
2. Secure Broken Glass: If the glass is cracked or shattered, apply tape (painter’s or duct tape) across the breaks in an ‘X’ pattern. This helps hold pieces together during removal.
3. Prepare Work Area: Clear the area around the window. Lay down drop cloths inside and outside if possible.

Step 2: Remove the Damaged Glass

The method depends on your window frame material (wood, vinyl, or aluminum). You may be able to do this with the sash still in the window frame, or you might find it easier to remove the bottom window sash first.

For Wood Frames:

1. Soften Old Glazing Putty (Optional): If the putty is very hard, gently heat it with a heat gun on a low setting (don’t scorch the wood or crack nearby glass!). This can make removal easier.
2. Remove Glazing Putty: Use a stiff putty knife or chisel to carefully chip away the old, hardened glazing putty from around the perimeter of the glass.
3. Remove Glazing Points: Locate the small metal triangles (glazing points) embedded in the wood, holding the glass edge. Use pliers or the tip of a flathead screwdriver to gently pry them out.
4. Lift Out Old Glass: Carefully grasp the taped glass (wearing gloves!) and gently wiggle it free from the frame. If stuck, check for any missed putty or points. Place broken glass immediately into a sturdy container for disposal.

For Vinyl or Aluminum Frames:

1. Remove Glazing Beads/Strips: These vinyl or rubber strips snap into a channel around the glass. Find a starting point (often a corner or seam) and use a thin putty knife or flathead screwdriver to carefully pry the bead dehors of its channel. Work along the length. Note their orientation (top, bottom, sides) as they may differ slightly. Be gentle to avoid breaking them.
2. Cut Old Sealant/Tape: Look for double-sided tape or silicone sealant between the glass edge and the frame channel. Carefully cut through it with a utility knife.
3. Lift Out Old Glass: Gently lift the glass out of the frame. Suction cups can help with larger panes. Dispose of broken glass safely.

Step 3: Clean the Window Frame/Sash

A clean surface is crucial for the new glass and sealant.

1. Remove Debris: Scrape away tous remaining old putty, sealant, tape residue, and glass fragments from the frame’s channel (the groove where the glass sits). A chisel, scraper, or putty knife works well.
2. Inspect Frame: Check for damage (rot in wood, cracks in vinyl). Make minor repairs if needed. (See our window repair guide for tips).
3. Prepare Surface:
   • Bois: Lightly sand the channel smooth. If bare wood is exposed, seal it with primer or linseed oil and let it dry completely.
   • Vinyl/Aluminum: Wipe the channel clean with rubbing alcohol to ensure good adhesion for new tape or sealant.

Step 4: Measure for and Obtain New Glass

Accurate measurements are critical.

1. Measure Opening: Measure the largeur et hauteur of the frame opening where the glass sits. Measure in at least two places for both width and height.
2. Calculate Glass Size:
   • Subtract 1/8 inch from both the smallest width and smallest height measurements. (e.g., If opening is 24″ x 30″, order glass 23 7/8″ x 29 7/8″). This small gap allows for expansion and easier installation.
3. Order Glass: Take your final measurements to a local glass shop. Specify you need “single strength” or “double strength” glass (for single pane) or provide detailed IGU specs if replacing a double-pane unit. Consider ordering custom-cut replacement glass if standard sizes don’t fit.

Step 5: Install the New Glass

For Wood Frames:

1. Apply Bedding Putty: Roll glazing compound into thin ropes (approx. 1/8″ diameter) and press it firmly into the L-shaped channel around the entire frame where the glass will sit.
2. Set the Glass: Carefully place the new glass pane into the opening, pressing it gently but firmly into the bedding putty. Ensure even contact.
3. Insert Glazing Points: Press new glazing points into the wood frame against the glass every 6-8 inches using a putty knife or glazier’s tool. These hold the glass securely while the main putty cures.
4. Apply Face Putty: Roll glazing compound into thicker ropes (approx. 1/2″ diameter). Apply it around the perimeter, covering the glazing points and filling the space between the glass and frame.
5. Smooth the Putty: Using a clean putty knife held at a 45-degree angle, smooth the compound to create a neat, beveled edge. Remove excess putty from the glass.
6. Cure and Paint: Let the putty cure completely (can take days or weeks depending on the product/weather). Once cured, prime and paint the putty and any bare wood, slightly overlapping the paint onto the glass (approx. 1/16″) for a better weather seal.

For Vinyl or Aluminum Frames:

1. Apply New Tape or Sealant: Apply new double-sided glazing tape into the channel OR run a consistent bead of appropriate silicone sealant along the back edge where the glass will rest.
2. Use Setting Blocks (If Applicable): Place small rubber setting blocks at the bottom of the channel if the original window had them. These support the glass weight.
3. Set the Glass: Carefully place the new glass into the frame, ensuring it rests on the setting blocks (if used) and makes good contact with the tape/sealant.
4. Reinstall Glazing Beads: Snap the vinyl/rubber glazing beads back into their channels, usually starting with the bottom, then top, then sides. A rubber mallet can help seat them fully, but be gentle. Ensure corners meet cleanly.

Step 6: Final Cleanup

1. Clean Glass: Clean fingerprints and smudges off the new glass.
2. Reinstall Sash (If Removed): If you removed the sash, reinstall it following the reverse of the removal steps. Test its operation.
3. Dispose of Old Glass Safely: Handle broken glass carefully. Check local regulations for proper disposal – often requires wrapping securely or placing in a designated container.

Conclusion

Replacing broken single-pane glass in a single-hung window is a manageable DIY task with careful preparation and execution. For double-pane windows with broken glass or failed seals, replacing the entire IGU is necessary, which often requires ordering a specific unit and may be best handled by professionals. Always prioritize safety when working with glass. If unsure or dealing with complex windows, consult a professional glass repair service.