Replace a Broken Window Pane

If you need to replace a broken window pane in a single-glazed window, there is no need to call a glazier, as it is a fairly simple task as long as you follow some basic rules and work safely. Things can obviously get more difficult the larger the pane is and the higher up it is located.

Before you start removing glass and applying putty, you need to measure the opening where the glass will fit and have a new pane cut by a glass supplier. Make sure you measure the size of the actual rebate where the glass will sit, not the overall size of the frame. The glass supplier should be able to advise you what thickness of glass you need for the size of the opening and the type of frame, so make sure you have as many details as possible when getting the glass cut.

Replace a Broken Window Pane

Learn how to replace a broken window pane in easy steps. For this project, you will need a glass cutter, small pliers, chisel/putty knife, putty, the replacement pane of glass, glazing sprigs or tacks, and a small hammer.

Step 1: Removing Broken Glass

The first thing you need to do is to clear the frame of any remaining glass. Make sure you wear thick gloves and eye protection when doing this. Place a dustsheet on the ground both inside and outside of the window to catch any fragments of glass and then score all the way around the broken pane with a glass cutter, close to the putty.

Carefully tap the glass with a hammer to break it out of the frame, trying to keep the pieces as large as possible. Hopefully these will all be caught by the dustsheets.

Step 2: Removing the Old Putty

With the majority of the broken glass removed, you can start to remove the old putty around the frame. Using a sharp chisel or putty knife, cut away the putty, being careful not to damage the frame beneath. Remember that there will still be a strip of glass beneath the putty, so work in gloves.

With the putty all removed, discard any remaining glass and use pliers to pull out the old glazing sprigs or tacks. Brush away any dust and debris from the window rebates and, optionally, paint the exposed wooden frame with a coat of primer.

Fitting a Temporary Window Cover

If you need to leave the window without glass overnight or for any extended period, the safest way to temporarily fill the hole is with a piece of hardboard, cut to size and nailed into the frame using panel pins.

Alternatively, if you want/need to keep some light coming in, you can cut a small sheet of thick polythene and nail thin battens of wood around the edges to hold it onto the frame. If only leaving overnight, you can simply tape the polythene to the frame. Just be aware of the security issues caused by having an easily accessible window.

Step 3: Applying New Putty

Choose the correct putty for the type of frame you are working on. Linseed Oil or Acrylic Putty should be used for a wooden frame and Metal Casement or Universal Putty for a metal frame. With either type of putty, you should work it in your hands for a little to soften it up. Now run a thin bead of putty around the rebate and press it firmly into the corner. This bead of putty is to create a seal on the outside of the window pane, so it doesn’t need to be thick, just thick enough to achieve this.

Step 4: Inserting the New Pane of Glass

If working alone, get everything you will need (glass, small hammer, sprigs or tacks) ready and within easy reach of the window.

Working with gloves on, carefully lift and insert the new pane of glass into the rebate, pressing the edges gently into the putty bead (never press in the middle of the glass). Quickly, but carefully, use a small hammer to tap two or three sprigs or tacks into the frame so they hold the pane of glass in place. Alternatively, if you are working on a metal frame, bend the clips to hold the glass in place.

Now work your way around the frame, tapping more sprigs into place at regular intervals. The safest way to do this is to hold the spring flat against the glass, with the point touching the face of the rebate. Gently place the hammer flat against the glass and slide it along to hit the sprig and drive it in.

Make sure they are tapped in enough so that they will not show through the putty about to be applied, but that they do not get pushed beyond the edge of the pane of glass.

Step 5: Finishing Off the New Pane

Run a second, thicker bead of putty around the edge of the glass and press it in firmly against both the glass and the frame. Look at the surrounding window panes and try to judge how much putty to use so the new will match the old.

Using a wet putty knife, carefully bevel the putty so it matches the rest of the windows. Alternatively, you can choose to use beading to hold the pane in place, bevel the corners and use tacks to pin it in place. Use a punch to knock the heads of the tacks below the surface and finish off by painting or varnishing as required.

You will need to let the putty set for a while before you can paint it. Follow the manufacturers instructions for this. Check the outside of the window and make sure that no putty has squeezed out of the small gap between the glass and the frame. If it has, use a wet putty knife to smooth it and press it into the gap.