How to Replace a Broken Window Pane | Ask This Old House

Ask This Old House general contractor Tom Silva replaces a broken pane in a basement window

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Time: 2 hours
Cost: $30
Skill Level: Beginner

Tools List for Replacing a Broken Window Pane:
Utility knife
HEPA vacuum
Measuring tape
Framing square
Caulking gun
Putty knife

Shopping List:
Gloves
Safety glasses
P100 Mask
Single pane glass
Glass cutting kit
Latex glazing putty
Glazing points

Steps:
1. Remove the window from the frame.
2. Cut the glazing around the broken window pane using a utility knife. Wear gloves, safety glasses, and a mask to protect yourself from the glass and the potential for lead in the window. Hold a HEPA vacuum up to the window while you scrape out the glazing to keep the dust down.
3. Once the glazing has been cut, carefully pry the old glass pane from the frame.
4. Measure the opening for the window pane and transfer those measurements to the new glass. With a wood frame, shave 1/16” off the measurement to allow for expansion and contraction of the wood.
5. Dip the glass cutter in the oil that comes with the kit and then score the glass along the measured line. Use a framing square or another straight edge to line up the measurements on the glass. Only score it once.
6. Hold the glass over the edge of the work surface, lift it up, and then snap the glass down on the edge of the surface. The glass should cut cleanly.
7. Load the glazing putty in the caulking gun. Apply the glazing to the window opening.
8. Gently place the cut glass into the frame on top of the window glazing.
9. Slide multiple glazing points into the frame on top of the glass. A putty knife should help get them into the perfect position.
10. Apply a second bead of glazing putty on top of the window into frame. Smooth out the lines with a putty knife.
11. The glazing will take a couple of days to fully dry, but the window can be placed back in the opening while it does.
12. Once it fully dries, take a razor blade and clean up the edges of the glazing.

Resources:
Tom demonstrated how to replace the pane of a single pane, basement window. His technique will only work with that type of window. For double and triple pane windows, the whole unit will need to be replaced.

The materials Tom used for this project, including the window glazing, glazing points, replacement glass, and glass cutters, are all available at home centers.

About Ask This Old House TV:
Homeowners have a virtual truckload of questions for us on smaller projects, and we're ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers—and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O'Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.

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How to Replace a Broken Window Pane | Ask This Old House
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