How to Fix Window Glass

You can identify some glass by how it breaks or how it reflects light:

• Annealed glass breaks in sharp shards. It’s relatively simple to find clear, annealed replacement glass.
• Tempered glass is stronger and breaks into small fragments rather than shards.
• Identify low-E glass by holding a flashlight to the window and note a pair of reflections on each pane. A low-E pane gives one of the reflections a different color. 

Glazing refers to window glass assembly:

• Single-pane windows contain a single glass sheet or several single panes.
• Multi-pane windows have an assembly of two or three glass sheets. Repair requires a complete insulated glass unit (IGU) from the manufacturer. Consider a pro if you need to repair multi-pane glass.

Glass may also have a tint you need to match. See our window glossary for more details on windows, glass, energy factors and more.

Protect yourself from broken glass with safety glasses and heavy-duty work gloves or cut-resistant gloves, long sleeves, long pants and closed-toe shoes. Wear a respirator to protect yourself from dust and mold. You also need this gear when scraping or sanding glazing compound or paint. In addition:

• Before beginning work, apply painter’s tape over the glass from corner to corner and be sure to cover any cracks. This helps keep the glass together.
• Some window glass repair requires working on a ladder. Follow the ladder manufacturer’s safety instructions.
• Windows can be heavy and unwieldy. Enlist a helper when removing or positioning window components.

Call a professional if:

• You’re not comfortable with the project.
• Exterior work is necessary on a multi-story home.
• You need to work from a ladder and aren’t experienced working at heights.
• You’re not sure how to safely remove the glass.
• You need to replace a large pane of glass.
  

It’s easier to replace broken window glass if your remove the sash — the framework that holds the glass — so you can work on it on a level surface. For some windows it might be a necessary step. Here’s how to remove several types of sashes:

• Single- or Double Hung Window With Sash Weights: Remove the interior stops. Pull one side of the sash away, hold onto the cord on the side and disconnect it from the sash. Maintain a grip on the cord and tie a knot at the end so the weight doesn’t pull the cord up into the frame. Repeat for the other side. Remove the parting stops and follow the same procedure for the upper sash, if necessary.
• Tilt-In Single- or Double-Hung Window: Release the tilt-in latches and tilt the sash inward until it’s horizontal. Lift one side up, pull it inward to release it from the slider or shoe on one side. Remove the sash from the other shoe. Repeat for the upper sash, if necessary.
• Non-Tilt-In Hung Windows With Spiral Tensioning Balancers: Raise the sash and install a clamp or set of locking pliers to support it. Unwind the balancer to remove the tension and disconnect the balancer. Repeat for the other side of the window. Lift the sash a bit to free it from the sliders, tilt it inward and remove it from the frame.
• Slider Window: Open the sash halfway and lift it from the bottom track. Tilt the bottom inward and lower the sash to remove it from the top track.
• Casement Window: Open the sash and use a screwdriver to pop the operator arms from the sash pivot and slider. With a helper supporting the window, pop the bottom hinge and then the top hinge off the frame pivots. Slide the sash out of the tracks.

Once you remove the sash, place it on a work surface that’s covered with a canvas drop cloth.

Here are the basic steps for fixing single-pane glass in a wood window:

1. With the sash flat on a work surface, carefully remove the existing glazing compound and any glazier points that secure the glass and the broken glass. You might need a heat gun to soften the compound enough to remove it with a paint scraper.
2. Remove the broken glass and dispose of it properly.
3. Clean the area around the pane thoroughly to remove any debris, paint or glazing compound so the new compound adheres fully.
4. Measure the thickness of the glass. Measure the opening in the sash and subtract 1/8 of an inch from the width and height. Get replacement glass cut to the adjusted measurements. Having the glass slightly smaller than the opening allows room for the wood frame and muntins to expand and contract with temperature and humidity changes.
5. Dry fit the glass.
6. Apply new glazing compound around the opening and set the glass in place, working it fully into the compound.
7. Press glazier points into the muntins to secure the glass in place.
8. Apply another bead of glazing compound over the glass and glazier points and use a putty knife to shape the compound evenly around the muntins.
9. Reinstall the sash and allow the glazing compound to dry fully before opening the window. Trim away any excess compound.
10. This is a good time to scrape away loose and peeling paint from the window and apply a new coat of paint. Wear safety glasses and a respirator when removing the paint. Mask the glass and prime the surfaces before painting.
    

These tips outline common steps for fixing single-pane glass in an aluminum window:

1. Carefully pry away the trim or glazing bead pieces from around the window. If they’re broken or damaged, order new pieces.
2. Use a utility knife to cut away the sealant around the glass. If necessary, disassemble the aluminum frame by removing screws in opposing corners of the frame.
3. If there are vinyl strips sealing the glass to the frame, remove them. It’s a good idea to order replacements to ensure a good seal with the new glass.
4. Measure the width and height of the glass and carefully remove it and dispose of it according to the guidelines for your area.
5. Measure the thickness of the glass. Use your measurements to have new glass cut.
6. Clean away any sealant or debris to improve adhesion of the new sealant.
7. Your window likely has glazing blocks or strips between the glass edges and frame to support the glass. Remove and clean them, then set them aside.
8. Dry fit the new glass.
9. Apply a bead of silicone sealant around the frame with no gaps.
10. Set the glazing blocks in place and install the new glass. Carefully press around the perimeter to ensure good contact with the sealant.
11. Replace the vinyl strips, if necessary, and the glazing beads.
12. Reinstall the sash. Allow the sealant to cure before opening the window.
    

Replacing multi-pane glass is best left to a professional to protect your warranty and to ensure energy efficiency. However, these general steps outline the common process for replacing a multi-pane, insulated glass unit (IGU) in a vinyl frame:

1. With the sash on your work surface, pry away any trim or glazing bead components. If they’re broken, you need to order new parts from the manufacturer.
2. Cut the silicone sealing the IGU to the frame with a utility knife.
3. Measure the width, height and thickness of the multi-pane glass or IGU and note the number of glass sheets. Order your replacement.
4. Carefully remove the broken glass unit and remove the vinyl band around the glass, if applicable. If it’s in good shape you can reuse it. Order a new one from the manufacturer, if necessary. Dispose of the broken glass properly.
5. Remove the glazing blocks or spacers, clean them and set them aside.
6. Clean the frame to remove residue and debris.
7. Install the vinyl band around the new glass, if necessary. Replace the spacers and dry fit the glass unit.
8. Remove the glass and run a continuous bead of silicone around the frame.
9. Place the new IGU in the frame, orienting interior and exterior faces correctly. Ensure the IGU engages fully with the silicone.
10. Replace the glazing beads.
11. Reinstall the sash and allow the silicone to set fully before opening the window.