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Many homes in the UK now have windows, which are double-glazed, but there are still many single glazed glass panels in wooden window frames to be found.  If a glass panel in such a frame is damaged, the cost of replacement could be expensive.

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Replacing A Broken Window Pane


Most homes in the UK now have windows which are double-glazed, but there are still many single glazed glass panels in wooden window frames still to be found.  If a glass panel in such a frame is damaged, the cost of replacement could be expensive, despite this, there are many who are reluctant to tackle this work themselves.  The reasons can range from; simply not knowing where to begin, to not knowing how to cut glass.
In this article, I will outline the process of removing and replacing a broken windowpane.

Health and Safety

Due to the sharp edges of glass, suitable gloves should always be used when handling, and as there is a danger of flying particles, safety glasses should also be worn.
Before beginning any work envolving broken glass, place a dust sheet on the floor on the inside of the room, and one on the ground below the window on the outside, so that broken glass is easily contained, and removed for disposal simply by lifting the sheets. In addition to this, have a suitable container close by; so that the larger pieces can be throw directly into it.
Removing broken glass requires care, especially when working above ground level. In such a case, place obstructions around the area and warn others to keep children and pets away. Where possible remove sashes from frames.
For domestic use above 800mm there are guidelines for glass thickness, which varies with the size of the panel, and for window frames to which the glass is to be fitted is less than 800mm from the ground level, then safety glass should be used. Your glass supplier will be able to advise you when you purchase the glass about the current regulations.


Before removing the broken or cracked glass preparation should be made by measuring for the replacement glass panel. To do this, measure the glass opening, so that the replacement panel can be cut and is ready to fit after the old pane is removed.  Simply measure the height and width of the opening (a tight fit), and then take these measurements to your local glass supplier. Ensure to inform the cutter that these are the 'tight size' of the opening, so that allowances can be made, so that the glass when fitted will have the essential gap all round its perimeter. If the glass panel is quite large, you could arrange delivery, to which there would be a small charge.  The glazier will also provide you with the correct grade, and amount of putty for the job, but be sure to tell him that the glass is being pointed.

Putty glazing 

Glass is held in the rebate of a window frame with putty and small nails or panel pins. Before a broken pane of glass can be completely removed all putty and fixings around the outside edge of the glass will need to be removed. Removing the old putty can be an arduous task, but a job that has to be done. To remove the putty, use a hacking knife, this resembles a conventional knife but is made using a very strong and thick metal, which allows the Hacking Knifeback of the blade to be driven into the old putty with a hammer. I find that an old wood chisel is also handy for removing stubborn bits up to the rebate. Remove the old pins with pinchers, or, if not accessible, punch them below the surface. Then, using a hammer, carefully knock out the glass from the inside; stubborn pieces can be spriest out with pinchers or pliers, working always from the top, so that loose bits do not fall onto your arms or hands. Once this is done, clear the putty from behind where the glass was; you should now be down to the wood.

Putty is never ready to use straight out of the pot, so will first need to be prepared. To do this, remove a suitable amount from the container and knead it in your hands until it is soft, pliable and easy to work. This is very important, as hard or lumpy putty makes it difficult, if not impossible to work with. Continue doing this until a sufficient amount to complete the task is of the same consistency.  If the putty is too oily, wrap it first in newspaper to absorb some of the oiliness.

With a ball of putty in the palm of the hand, introduce it into the rebate using the thumb, and lay a continuous strip of bedding putty about 6mm thick all round the back of the rebate against which the glass will be placed. With the fixing pins and hammer to hand, place the glass into the rebate, bottom first, leaving an equal space all round the edges, and press it gently (from the edges) against the back putty, squeezing out the surplus putty until a thickness of about 2mm remains between the glass and the rebate, then place some packing pieces beneath it so that it does not slide down.

To fix the glass in place, tack panel pins into the side of the rebate, against the face of the glass, and using a small hammer, knock the pins in, and at the same time, keep the hammer touching the glass as you work, so that you do not knock the glass and break it. The pins should be driven into the rebate, while up to the glass and driven in vertically. A strip of weathering putty must now be placed around the outside of the pane.

Knead the putty in the hands as before, and lay a thick continuous strip into the angle of the rebate against the face of the glass. Lubricate the knife with water to keep the putty from sticking to it, and hold the putty knife in one corner of the window with the blade against the rebate and the tip resting on the glass at an angle, and cut the excess putty off all round the pane in one clean stroke, so that a slope is formed to allow the rainwater to run off, and tidy the corners with a square-ended putty knife to form a mitre. It may be necessary to do this a few times to get a consistent thickness of putty all around the glass.

After two to three weeks, the putty may be painted over, using an oil based undercoat and finishing coat to match the existing paintwork.

Top Tip: When re-painting, allow the brush to run over the putty and onto the face of the glass by about 3mm, as this will form a waterproof seal between the two materials.
1. Remove Putty
2. Remove Pins
3. Apply Putty
4. Secure Glass
5. Apply Putty
6. Point Putty


Detail showing glass panel in rebate with putty bed to underside and rear of the glass. Also showing pin inserted vertically so as not to damage glass.
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