Replacing a Broken Pane

This describes how to replace a pane of glass in a wooden frame. Follow the same technique with a metal frame but don't add metal glazing sprigs. Get a professional to replace a pane in a uPVC frame.

1. Remove the old glass, making sure that you're wearing safety goggles, thick gloves and boots for protection. Lay down either an old sheet or newspapers outside the window to catch the fragments. You may need to use a hammer and old chisel to knock out the smaller pieces.
2. Measure up (height and width) for the replacement glass, using millimetres for accuracy. Take a couple of measurements at different points along the window rebate (the recess for the glass, around the inside of the frame), as the frame may not be square and the new glass will crack if it is too tight a fit. Use whichever measurement is the smaller in each case, and subtract 3 mm from both height and width to allow for movement.
3. Wearing stout gloves, use a chisel and hammer to chip the putty out of the rebate Make sure you use an old chisel, as the sprigs (small headless tacks used to hold the glass in) will blunt a new one.
4. Lever out the glazing sprigs with pliers. If bare wood is visible around the rebate, give it a generous coat of wood primer and leave to dry (see tin for advice on how long). Treat rot first with wood hardener and filler.
5. Knead some putty in your hands to make it soft and workable. If the putty is wet and sticky, roll a handful on newspaper to absorb some of the linseed oil. Form it into a sausage shape of about 20 mm (3/4 in) diameter and press into place all round the rebate, with no gaps.
6. Rest the bottom edge of the pane on the lower edge of the rebate and lift the glass upright, pressing the pane in around all edges to squash the putty and make a weatherproof seal.
7. Tap new glazing sprigs into the edges of the rebate at about 150 mm (6 in) intervals. Slide the side of the hammer head up and down against the glass as you gently tap them in to avoid sudden knocks.
8. Press in more putty and use a putty knife to form a neat slope of about 45° between the glass and the frame. Some putty will squeeze out of the rebate, so trim off excess from inside the window. The putty will harden in about 14 days.