Replacing a broken windowpane is a job you can easily do yourself.
Removing the Old Pane
Wearing a pair of heavy work gloves, wiggle the broken pieces of glass back and forth to loosen and remove them from the frame, if they don’t come loose easily.
Knock the pieces out with a hammer
With a chisel or scraper remove all the old putty. bit by bit. Don’t try to force long pieces out.
Soften stubborn chunks with a propane torch or soldering iron, or paint the old putty with linseed oil, let the oil soak in, then scrape again.
If you’d prefer to watch a video on replacing broken window panes rather than reading text, here is a helpful one from “This Old House”:
Glazier’s Points and Spring Clips
If the window frame is wood, look for glazier’s points (small metal triangles) as you work.
In metal frames, look for spring clips. Remove them carefully and set them aside.
If points or clips are missing, get some when you buy the glass.
Prepare for the New Pane
Wire-brush the frame to remove all the traces of old putty.
For a wood frame, coat the raw wood where the old putty was with linseed oil, all around the frame, and let the oil soak in completely.
Measure the inside of the frame carefully in both directions, subtracting 1/16 inch each way to allow for natural expansion and contraction and for any irregularities in glass or frame.
If the lip of the frame is very wide.
You can subtract as much as 1/8 inch from each dimension.
Have the glass cut to size at a hardware store or lumberyard.
Install the New Pane
With the glass at hand, remove a large chunk of putty from the can.
Roll the putty between your palms, shaping it into a narrow, roughly pencil-size roll.
Press the putty roll around the inside of the empty window frame, starting at a corner, where the glass will be pushed into place.
Working carefully, press the new pane of glass firmly against the putty pushing hard enough to force some of the putty out around the glass and to remove any air bubbles.
Insert the spring clips (metal frame) or glazier’s points (wood frame).
Snap the clips back into their holes.
Use the putty knife to insert glazier’s points into the wood frame, pushing in the sharp points every 6 inches or so around the frame.
Before going any further, look at adjacent or nearby windowpanes. The new putty should match the putty on these panes
To apply putty to the outside of the new pane, make another putty roll Press it firmly all around the new glass.
Press hard enough so that there are no gaps
Dip the putty knife in linseed oil and shake off the excess Using long, even strokes, smooth the putty around the new pane.
It should not be visible over the frame on the inside of the window.
Use a razor blade or glass scraper to remove any excess putty on both sides of the glass and frame.
Let the new putty cure for three days before painting it.
If the surface of the putty is very rough, Smooth it carefully with fine sandpaper.
You don’t have to repaint the whole window frame, but let the paint overlap a little onto both frame and glass, to make sure the putty is sealed at both edges.
Use two coats and let the paint dry thoroughly before cleaning the glass.
More Tips on Replacing a Window Pane
- To calculate the size of a replacement pane of glass, measure the inside height and width of the sash, then subtract 1/8 inch from each dimension
- Panes of glass in modern sashes may be installed with special moldings, clips, gaskets or sealants. To be sure that replacement materials are compatible with both the new pane of glass and the sash, take along samples of the old materials to a window pane deal or building supply center.
- As a stopgap measure when a broken pane of glass cannot be replaced immediately, clear away loose shards and fragments, then tape cardboard or heavy plastic in place over the opening in the sash.
Step-By-Step Instructions for Replacing a Window Pane
- Wearing Work gloves, pull shards of glass out of the sash, gently wiggle stubborn fragments to free them. Place the broken glass in a cardboard box for disposal.
- Pry glazing compound out of the sash with a putty knife. Soften hardened compound, if necessary, by heating it with the tip of a soldering iron.
- Pull glazier’s points out of the sash with long-nose pliers. Clean the sash channel using a wire brush, then smooth it with medium sandpaper.
- Prepare the sash channel for putty-type glazing compound by brushing it with linseed oil.
- Line the sash channel with a thin bead of glazing compound, rolling a small amount at a time into a snake-like shape and pressing it into place.
- Wearing work gloves, carefully set the replacement pane of glass into the bed of glazing compound in the sash channel, make sure that it is seated snugly.
- With a putty knife, press glazier’s points halfway into the sash and snug against the pane of glass at intervals of 4 to 6 inches.
- Press glazing compound into the sash channel along each edge of the pane of glass, beveling it at a 45 degree angle and embedding the glazier’s points.
- Smooth and shape the glazing compound with the wet blade of a putty knife. Wipe off excess compound and let it set; when it no longer shows a thumbprint, apply paint or varnish,
When buying glass, tell the supplier the size of the panes. He’ll advise on the thickness of glass you should use and will cut them to fit.
The first step to replacing a broken window pane is removing what’s left of the old glass. Wear gloves and work slowly to avoid cuts. Then, scrape out the old glazing with a putty knife and measure the opening for the new pane of glass, which should be slightly smaller than the opening so it fits in easily.