Replacing a broken single-glaze pane is messy and requires attention to detail, but with a bit of practice you can learn to install the glass safely and make smooth glazing lines. Your technique will depend on what kind of window pane you have. A wood frame takes more steps to repair but allows you to maintain the vintage character of your home. A vinyl frame is likely from a new home and is much easier to work with. We have tips for repairing the glass in both kinds of window frames below.
Before You Begin: Tips for Buying and Cutting Glass
In most cases it is best to have a local hardware store or glass specialist cut the glass for you. Unless the pane is very small, order double-thick glass; single-thick glass breaks easily. In a door, sidelight, or other high-traffic areas, order shatter-resistant glass.
Be sure to wear thick gloves, long clothing, and protective eyewear when handling shattered glass. Tiny, nearly invisible splinters can cause injury.
Traditional glazing putty (also called glazing compound) is applied with a putty knife. You can also buy glazing putty in a caulk tube, but applying with a knife creates a tighter bond and a smoother surface once you get the hang of it.
Often it is possible to replace double-glaze panes yourself; see the most common types of installation. In some cases you may need to take the sash into a hardware store or glass specialist for repairs.
What You Need
- Tape measure
- Paint scraper
- Glazier's putty knife or standard putty knife
- Wire brush
- Heat gun
- Glass cutter
- Glass pane to fit
- Glazing points
- Glazing compound (putty)
- Linseed oil
Replacing Glass in a Wood Frame
Step 1: Remove Glass Shards
Usually you can replace glass while the sash is still in the frame, but it is easier to remove the frame first and work on a table. While wearing protective clothing, wiggle and pull out the shards of glass. You may need to tap the glass with a hammer to create a new break line first.
If the glass does not easily pull out in pieces, apply a grid of duct tape to the pane. Use a heat gun and scraper or chisel to remove all the putty and points, and pull the pane out in one piece.
Step 2: Remove Putty and Glazing
Take care to remove all pieces of glass, putty, and metal glazing points. You may need to use a pull-type paint scraper or an old chisel. If you use a hammer, tap gently. The grooves where the new window will go must be completely smooth. A heat gun can help soften the old putty.
Step 3: Prep Frame
Wire-brush the frame and vacuum or wipe with a slightly damp rag. Apply a coat of linseed oil to the rabbet; this helps the putty stick securely.
Step 4: Measure Pane
Carefully measure the height and width of the opening in at least two places. Order a piece of glass 1/8 inch shorter in each direction. Test-fit the pane before proceeding.
Step 5: Apply Putty
Roll a ball of glazing compound into a thin rope. Press it into the corner of the rabbet. Then use a putty knife to press it firmly into place, making a thin bed of putty for the glass to rest against.
Step 6: Check Glass
Gently press the glass into the putty bed, checking that it lies flat against the rabbet in all places. Every 6 inches or so, press a glazing point into the wood; push only gently against the glass as you go.
Step 7: Roll Putty
Roll a rope of putty about 3/4 inch thick. Aim for a fairly uniform diameter, but it need not be perfect.
Step 8: Apply Putty to Glass
Press the rope against the glass and the frame, using your thumb. Using a rag to periodically apply linseed oil to a glazier's knife or putty knife, press again using swiping motions every inch or two.
Step 9: Smooth Putty
Working in the same direction and holding the knife at the correct angle so the putty will not be visible inside, press firmly and draw the knife along the line to smooth the putty.
Step 10: Finishing Touches
If the resulting putty has a series of slight ridges, smooth them by lightly wiping with your finger, working in the opposite direction as in step 9.
How to Reinstall Wood Molding
If a pane is secured with pieces of wood molding, pry the molding out with a small flat pry bar. Scrape away any old caulk, test the fit, and apply new silicone caulk. Press the pane into the caulk. When reinstalling the wood molding, take care to angle the nails so they do not touch the glass. Reuse the old nail holes, perhaps driving slightly larger nails. Use a scrap of plywood to protect the pane.
Replacing Glass in a Vinyl Frame
Step 1: Remove Stop
Use a putty knife or small flat pry bar to remove the vinyl stop. Work carefully, to avoid cracking the stop. Remove the glass and order a new piece to fit.
Step 2: Replace Sealing Tape and Sealant
Test to see that the new pane will fit. Scrape away the old sealing tape and clean the surface with paint thinner. Cut pieces of sealing tape to fit precisely and press them into place on the rabbet. Just before installing the glass, spread a bead of silicone sealant onto the rabbet.
Step 3: Place Glass
Carefully set the pane in place—you cannot adjust its position once it is set into the tape. Press the vinyl stop back into the frame to secure the glass.
How to Install a Rubber Gasket
If your pane is held in place with a rubber gasket, slip the gasket onto the edges of the glass, pressing firmly so the gasket is tight at all points. Then set the pane into the frame. You may need to partially disassemble the frame first.
Types of Glazing for Thermal Panes
Double-glazed windowpanes must be produced by a professional; you cannot cut them yourself. They are secured in a variety of ways. Here are the three most common methods. If the techniques on the opposite page do not apply to your situation, take the sash to a shop to have the glass replaced.
Sealing tape usually needs to be replaced. Rubber gaskets can often be reused, but only if they are unbroken and have not dried and become brittle. Caulking needs to be scraped away and replaced. Wood molding can usually be reused, but you may replace it with new molding.