Replace a broken window pane
To replace a broken window pane in an older wood window, you take out the broken glass and the old glazing putty, fit a new pane, hold it in place with small metal glazier's points, and seal it with fresh glazing compound. It's slow, careful work more than hard work. Newer vinyl and double-pane windows are different: their glass is a sealed unit held in by snap-in strips, and you order a replacement unit from a glass shop instead. Old windows were built to be reglazed. Points hold the glass; putty seals it.
How window glass is held in
In a traditional wood window, each pane sits in a small recess in the frame called a rabbet. Thin metal glazier's points pushed into the wood keep it from falling out, and a bead of glazing putty seals it and sheds water. The putty dries and cracks over the years, which is why old windows rattle and leak air.
Double-pane windows are built differently. The two layers of glass are sealed together at the factory into one insulated unit and held in by strips called glazing stops. If one of those breaks, or fogs up between the panes, the unit is replaced as a piece. Knowing which kind you have decides the whole job.
Why panes break
A ball, branch or slammed sash breaks the glass.
The glass loosens and rattles.
Sticking sashes and settling twist the frame.
Double-pane units fog between the panes.
| You see | Type | What to do |
|---|---|---|
| Hard putty around the glass | Single pane, glazed | Steps 3 to 9 |
| Snap-in strips, two layers of glass | Sealed double-pane unit | Order a new unit (Step 2) |
| Fog between two layers | Failed seal | Order a new unit (Step 2) |
| Glass rattles but isn't broken | Old putty | Steps 1, 4, 5, 7, 8 and 9 |
Let's fix it
- Make it safePut on heavy gloves and safety glasses. Lay a drop cloth below the window. Crisscross duct tape over cracked glass so it holds together. In a home built before 1978, test the paint and old putty for lead before scraping.
- Check what kind of window it isLook at how the glass is held. A bead of hard putty around the outside means a single pane held with glazing compound, which this guide covers. A plastic or wood strip that snaps or screws in, and two layers of glass, means a sealed double-pane unit. For those, measure the glass and take the measurements, or the sash, to a glass shop for a replacement unit.
- Remove the broken glassWorking from the outside, wiggle out loose pieces from the top down and put them straight into a sturdy box. Leave pieces stuck in the putty for the next step. Never push on cracked glass with bare hands.
- Remove the old putty and pointsSoften stubborn putty with a heat gun on low or a hair dryer, keeping it moving and away from the glass, and scrape it out with a stiff putty knife. Pull the old glazier's points with needle-nose pliers. Clean the rabbet down to bare wood and remove every bit of old glass.
- Prime the woodBrush linseed oil or a primer onto the bare wood in the rabbet and let it soak in. Dry wood pulls the oil out of new glazing compound, which makes it crack early.
- Measure and get the glassMeasure the opening side to side and top to bottom in a few places, and use the smallest numbers. Subtract about 1/8 inch from each so the glass has a little room. Have a hardware store or glass shop cut it, and ask for the same thickness as the old pane.
- Bed the glass and set the pointsRoll a thin rope of glazing compound and press it into the rabbet as a bed. Set the new glass in and press around the edges, not the middle, until it beds evenly. Push glazier's points into the wood every 4 to 6 inches, with at least two per side, using a point setter or the side of a putty knife, so they hold the glass without pressing on it hard.
- Glaze the outsideRoll more glazing compound into a rope and press it along the edges of the glass. Draw the putty knife along it at an angle to make a smooth, sloped bevel from the glass to the wood. Keep the putty line slightly below the inside edge of the frame so it can't be seen from inside. Scrape off the extra.
- Let it cure and paintLet the glazing compound skin over for the time on the label, often a week or more. Then paint it, lapping the paint about 1/16 inch onto the glass to seal the joint. Clean any compound smudges off the glass.
Watch it done
- The glass is snug and doesn't rattle
- The putty bevel is smooth
- Paint seals onto the glass
If the window sticks
If the screen is torn, check our guide for repairing a window screen.
If the window sticks after the repair, check our guide for a window that sticks or won't open.
If the wood under the glass is soft, there's a separate guide for repairing a rotted window sill.
What a pro typically charges (a rough estimate; prices vary by area): A glass shop or handyman typically charges $100–$300 to replace a single pane, and more for double-pane units or large windows.
Find a handyman near youSomething else going on?
Window pane questions
Can I replace a window pane myself?
Yes, on a single-pane wood window. Double-pane units are usually ordered from a glass shop.
What holds window glass in place?
Small metal glazier's points, sealed with glazing compound.
How long does glazing compound take to dry?
It varies by product, often a week or more before painting. Check the label.
How do I measure for replacement glass?
Measure the opening in a few spots, use the smallest, and subtract about 1/8 inch from each measurement.
Can I reglaze a window myself?
On an older single-pane wood window, yes. Remove the old putty and points, prime the wood, set the glass with glazier's points and glaze the outside.