Broken Window Repair: A Complete Guide to Fixing or Replacing Window Glass
A broken window is a household emergency. Beyond the immediate mess of shattered glass, a broken window compromises your home’s security, energy efficiency, and weather protection. Every hour that a window remains broken allows heat to escape, moisture to enter, and potential intruders to access your home. While the prospect of replacing window glass may seem daunting, single-pane windows are surprisingly straightforward to repair yourself. Double-pane and specialized windows are more complex and often require professional help.
The Problem: Immediate Concerns
Safety First
The first priority when a window breaks is safety. Keep people and pets away from the broken area. If the glass is still partially intact but cracked, do not try to remove it by hand. Wear thick work gloves and safety glasses before approaching the broken window. Lay a tarp or heavy drop cloth below the window to catch falling glass. For upper-floor windows, clear the area below the window to prevent injury from falling debris.
Temporary Emergency Fixes
Before attempting a permanent repair, secure the window to restore security and prevent weather damage. For a broken pane where the frame is intact, measure the opening and cut a piece of thick cardboard or plywood slightly larger than the opening. Tape or screw it in place from the inside. For windows with minor cracks, apply clear packing tape to both sides of the crack to prevent it from spreading and to maintain some insulation. For windows in doors or at ground level where security is critical, consider a temporary security bar or board.
Types of Windows
Single-Pane Windows
Single-pane windows are the simplest design: a single sheet of glass held in place by glazing compound (putty) and small metal clips called glazing points. These windows are common in older homes and are the easiest to repair. Replacement involves removing the old putty and glass, preparing the frame, installing new glass, and applying new putty. Single-pane glass is inexpensive and available at any hardware store.
Double-Pane Windows
Double-pane windows consist of two panes of glass separated by an air gap filled with insulating gas. When one pane breaks, the insulating seal is compromised, and the window loses its energy efficiency. Double-pane window repair is more complex because you must replace the entire sealed unit, not just the glass. The unit is typically held in place by stops or retaining clips that must be carefully removed. Replacement sealed units must be custom-ordered to your window’s dimensions.
Specialty Glass
Tempered glass, used in doors and near floors per building codes, shatters into small, relatively harmless pieces. It cannot be cut to size and must be ordered as a custom piece. Laminated glass, used in hurricane zones and for security, has a plastic layer between panes that holds the glass together when broken. Both types require professional measurement and replacement.
Step-by-Step Single-Pane Window Repair
Remove the Broken Glass
With heavy gloves and safety glasses, carefully remove loose glass pieces starting from the top and working down. For glass that is cracked but not falling out, use a hammer to gently tap around the edges to release pieces. Use glazier’s pliers or needlenose pliers to remove remaining glass shards from the frame. Dispose of glass in a rigid container clearly marked as broken glass.
Remove the Old Glazing Compound
Old glazing compound becomes hard and brittle over time. Use a putty knife, chisel, or heat gun (on low) to soften and scrape away the old putty. A glazier’s bar or stiff putty knife helps pry out stubborn material. Remove all old glazing points — the small metal triangles that held the glass in place. Sand or scrape the frame to bare wood and apply a coat of linseed oil or wood primer to protect the exposed wood before installing new glass.
Measure and Cut the New Glass
Measure the frame opening at multiple points, subtract 1/8 inch from each dimension to allow for expansion, and have the glass cut at a hardware store or glass shop. For most single-pane repairs, standard window glass is appropriate. If you are comfortable scoring and cutting glass yourself, you can buy a glass cutter and cut the pane to size, but having it professionally cut is inexpensive and eliminates the risk of breakage.
Install the New Glass
Apply a thin layer of glazing compound to the frame to create a bed for the glass. Press the new pane into place, pressing firmly around the edges to set it in the compound. Insert glazing points every 6 to 8 inches along each side, using a putty knife to push them into the wood. The points should hold the glass firmly without pressing against it.
Apply New Glazing Compound
Knead the glazing compound to warm it and make it pliable. Roll it into a rope about 1/4 inch thick and press it into the angle between the glass and frame. Use a putty knife held at a 45-degree angle to smooth the compound into a neat, consistent bevel. Clean excess compound from the glass surface. Allow the compound to cure for one to two weeks before painting. Paint the putty to match the frame, which also protects the compound from cracking and extends its life.
Double-Pane Window Replacement
Double-pane replacement requires ordering a sealed unit. Measure the glass opening accurately. Remove the inner stops or retaining clips holding the existing unit. With help (the unit is heavy), carefully remove the old sealed unit. Clean the frame and install the new unit, using shims if needed to ensure proper alignment and level. Reinstall stops and clips. Apply silicone caulk around the exterior edge to seal against moisture. The home insulation guide offers guidance on improving window efficiency during replacement.
When to Call a Professional
Some window repairs are best left to professionals. Double-pane windows with failed seals (fog between panes) require replacement of the entire sealed unit. Specialty glass like tempered or laminated glass must be custom-ordered and installed with specific techniques. Windows in unusual shapes or sizes, or windows that are part of a historic structure, require specialist knowledge. Upper-floor windows that are difficult to access safely should be handled by professionals with proper equipment.
FAQ
How much does it cost to repair a broken window?
Single-pane window glass costs $5 to $15 per square foot, plus $10 to $20 for glazing compound and points. Total DIY cost for a standard window is $20 to $50. Professional single-pane repair runs $100 to $250. Double-pane sealed unit replacement costs $150 to $400 for the unit plus $100 to $200 for professional installation.
Can I replace just one pane of a double-pane window?
No. Double-pane windows are manufactured as sealed units. When one pane breaks or the seal fails, the entire unit must be replaced. Attempting to replace only one pane would compromise the insulating gas and allow condensation between the panes.
How long does window glazing compound take to dry?
Standard glazing compound requires one to two weeks to cure before it can be painted. Cold, humid weather extends curing time. Some newer acrylic-based glazing compounds are paintable in 24 hours. Check the manufacturer’s instructions for specific drying times.
Should I caulk the exterior of a new window installation?
Yes. A bead of exterior-grade silicone caulk around the window frame prevents moisture infiltration. Apply caulk to the joint between the window frame and the surrounding wall structure. Do not caulk the weepholes at the bottom of the window — these allow moisture to drain.