How to Fix Broken Window Glass

A broken windowpane not only allows the weather into your home, it is also a security hazard. Luckily, broken glass is one of the easiest problems to fix. You can buy replacement glass, cut to measure, at lumberyards and hardware stores. Here's how to replace a broken pane in a single pane (one thickness of glass) window:

What You'll Need
Here are the tools you'll want to have on hand to replace broken window glass:
  • Safety goggles
  • Masking tape
  • Hammer
  • Heavy gloves
  • Chisel or scraper
  • Linseed oil
  • Clean cloth
  • Tape measure
  • Replacement glass
  • Glaziers' points or spring clips
  • Putty knife
  • Glaziers' compound or putty
  • Single-edge razor blade or glass scraper
  • Rust-resistant paint and paintbrush

Step 1: Wearing safety goggles, remove broken or cracked glass from window frame. To remove glass without excessive splintering, crisscross window pane on both sides with masking tape, then rap it with a hammer. Most of the pane will be held together. Wearing gloves, work any remaining pieces of glass back and forth until they're loose enough to pull out. Knock out any stubborn pieces with hammer.

Step 2: Remove all old putty from frame, using chisel or scraper to pry it out. As you work, look for fasteners that held glass in place -- metal tabs called glaziers' points in wood-frame windows; spring clips in metal frames. If putty doesn't come out easily, apply linseed oil to it, and let oil soak in. Then scrape out softened putty, being careful not to gouge out window frame.

Step 3: Apply linseed oil on raw wood around pane to prevent new putty from drying out too fast. If frame is metal, apply rust-resistant paint.

Step 4: Measure frame for new glass. It should be just smaller than opening to allow for expansion and contraction and to allow for imperfections in frame or glass. Measure both ways across opening, from inside edge to inside edge, and subtract 1/16 to 1/8 inch each way. Have double-strength glass cut to these precise dimensions. Purchase enough new glaziers' points or clips to be installed every 6 inches or so around pane.

Push glazier's points in at six-inch increments with a putty knife.
©2006 Publications International, Ltd.
Glazier' points hold the glass in place in a wood-frame window. Push
the points in with a putty knife.

Step 5: Install new glass using glaziers' compound or putty. Roll large chunk of compound between your palms to make long cord (about diameter of pencil). Starting at a corner, press compound into outside corner of window frame, where glass will rest. Cover entire diameter of frame. With compound in place, carefully set new pane of glass into frame, pressing it firmly against compound.

Press hard enough to flatten, squeezing out air bubbles and forcing some of the compound out around frame. Then, to hold glass in place, install new glaziers' points or spring clips every 6 inches or so around pane. Push points partway into wood with blade of putty knife held flat against glass; if the frame is metal, snap spring clips into holes in frame.

Step 6: To seal the new window pane with glaziers' compound all around the outside edge, roll another cord of glaziers' compound, and press it firmly into the glass-frame joint, all around the pane. Use putty knife to smooth compound all along the joint around the pane, matching putty to other nearby windows. Hold putty knife at an angle to lip of frame, so knife cuts compound off cleanly and evenly along glass. If putty knife sticks or pulls at glaziers' compound, dip blade into linseed oil, and shake off excess. Use long, smooth strokes to keep joint even around pane.

Metal-frame windows often use clips to hold the glass in place.
©2006 Publications International, Ltd.
Metal-frame windows often use clips to hold the glass in place.

Step 7: With razor blade or glass scraper, carefully remove excess glaziers' compound from both sides of new glass and frame. Let compound dry for about three days.

Step 8: Paint new compound and frame to match rest of frame. Lap paint slightly over edge of compound and onto glass to seal pane completely. Make sure paint is dry before you clean glass.

Additional Window-Repair Tips

No matter what type of window repair you might need to tackle, the additional guidelines below can help you get the job done quicker with less mess.
  • To prevent a windowpane crack from spreading, score a small arc with a glass cutter just beyond the crack, curving around it. Most of the time crack will travel only as far as the arc.
  • Before trying to chisel hardened putty from a wooden window frame, brush raw linseed oil over putty. Let it soak in to soften the putty.
  • Fill a pellet gun hole in a windowpane with clear nail polish or shellac. Dab at the hole; when the application dries, dab again and reapply until the hole is filled. The pane will appear clear.
  • To cover a clear bathroom window without putting up curtains, make the glass opaque by brushing on a mixture of 4 tablespoons of Epsom salts and 1/2 pint of stale beer.
Window screens sometimes become torn or bent and need to be tended to before they become an eyesore or security hazard. Learn how to repair and replace screens in the next section.