Replace Broken Window Pane

by Murray Anderson

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? Whatever broke your window, as long as it is a single pane of glass, you can fix it.

Here's what you'll need

Work gloves and eye protection
Masking tape
Towel
Hammer
Replacement glass
Long nosed pliers
Putty knife
Glazing compound (or putty)
Glaziers points
Chisel or screwdriver
Paint brush and fast drying primer
Tape measure

Getting the Broken Pane Out

Start by removing the window (more properly the window sash) and laying it on a flat surface large enough to accommodate it. Make sure you are wearing your eye protection and work gloves for the next step because you need to remove what's left of the windowpane.

If your window is cracked through but not broken you’ll need to break it. Criss-cross some masking tape across the window (to help prevent it shattering), put a towel over the glass and hit it with a hammer hard enough to break the glass. Now carefully wiggle out the broken pieces.

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 very firmly bonded to the window frame and you'll need to use a square headed screwdriver or an old chisel to scrape it away. Pull out any glazier's points (small triangular shaped pieces of metal - which held the glass in place) with your long nosed pliers. Finally, give the frame a quick sanding to remove any traces of glazing compound left. (The frame needs to be clean and smooth for the new glass to fit properly).

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.

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

Installing the Replacement Glass

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 also a water proof seal around the outside of the glass pane. Alternatively you can use linseed oil putty instead of the caulking to do the same job. 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. Now lay the replacement glass pane into the frame, pressing it down into the caulk or putty.

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

To finish sealing the window edge you need to roll a piece of glazing compound between your hands making a string about 3/8" 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.

Finishing up

Clean the new glass using turpentine or mineral spirits and put the sash back in place for a week so 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.

Metal windows

If your broken window is in a metal frame the above procedure will (in general) be the same for you, with just a couple of difference. First, you obviously don't need to worry about preventing your window frame from absorbing oil from the glazing compound and 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. You already know they're the right size and they can be reinserted into the existing (premade) holes in your metal frame.

That's it, as you can see repairing a broken glass pane isn't a difficult job, it's just a little time consuming. However, everything you need is readily (and inexpensively) available at your home store so why would you pay someone to just replace a single pane of glass?