How to Replace a Broken Window Pane

Did that budding pitcher in your family get a little wild with a "high hard one," or was it just a bird that tried to take a shortcut through your bedroom? Replacement windows can be pricey, so it's natural to worry about how you're going to fix it when something busts through the glass. However, you can easily fix your broken window as long as it's a single pane of glass.

Warning: When working with any broken glass, it’s important to take precautions. Wear both gloves and protective eyewear.

Step 1 – Remove the Broken Pieces

Start by removing the window sash, and place it on a flat work surface.

If your window is cracked but not broken, you'll need to break it yourself. Crisscross some masking tape across the window to help prevent it from shattering. Then, put a towel over the glass and hit it with a hammer to break it. Carefully wiggle out the broken pieces and dispose of properly.

Step 2 – Remove the Glazing and Glazier's Points

Next, you should remove the glazing compound around the perimeter of the windowpane. Sometimes it's so old that it just breaks off; but, unfortunately, it can also be firmly bonded to the window frame. If this is the case, you'll need to use a square-headed screwdriver or a chisel to scrape it away.

When you're finished, pull out any glazier's points (small, triangular-shaped pieces of metal that held the glass in place) with your long-nosed pliers.

Step 3 – Finish the Frame

Sand the frame to remove any traces of glazing compound left, as the frame needs to be clean and smooth for the new glass to fit properly.

Then, use a fast-drying primer to paint the exposed wood. This will seal the wood frame and stop the wood from sucking oil out of the glazing compound.

Step 4 – Measure the Window Opening

While the primer is drying, measure the size of your window opening and get a piece of replacement glass 1/8-inch smaller in both length and width. This will ensure that the glass fits easily into the opening.

Step 5 – Install the Replacement Glass

Caulk the Window Frame

Run a thin bead of clear caulk around the exterior of the window frame. The caulk will provide a nice cushion for the glass to sit in and will also serve as a waterproof seal around the outside of the glass pane.

Alternatively, you can use linseed-oil putty instead of caulking. Roll a small piece of putty between your hands to make a long, thin string, and then press it firmly into place using your putty knife. Then, lay the replacement glass pane into the frame, pressing it down into the caulk or putty.

Install New Glazier's Points

Next, install new glazier's points to hold the replacement pane firmly in place. Push the pointed end into the frame using your thumb, and then use a screwdriver to push them completely into the frame. You'll need glazier's points on all sides of the pane, about 2 inches from each corner and along the top, bottom, and sides of the window spaced at least every 8 inches apart.

Use Glazing Compound

To finish sealing the window edge, roll a piece of glazing compound between your hands to make a string about 3/8 inch in diameter. Use your fingers to press this string into the seam between the glass and the window frame. Use the flat edge of your putty knife to press it firmly into place and, then holding your knife at an angle between the glass and window frame, smooth down the surface.

Step 6 – Clean, Let Dry, and Paint

Clean the new glass using turpentine or mineral spirits and put the sash back in place for a week so that the glazing compound can dry thoroughly. Once the compound has dried, paint the frame to ensure the seam between the glass and the window frame is protected.

A Note About Metal Window Frames

If your broken window is in a metal frame, the above procedure will generally be the same for you with minor differences. First, you don't need to worry about preventing your window frame from absorbing oil from the glazing compound. Second, metal windows don't have glazier's points; they use metal clips to hold the glass in place. Save the metal clips that you took out of your window when removing the broken glass. They can be reinserted into the existing holes in your metal frame.