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Repairing a broken window - Part 2

Cost: Difficulty:


Always wear thick gloves and safety goggles when reglazing or repairing a damaged window containing broken glass.
A broken window is both a security risk and a safety hazard.

Using putty

Putty is a pliable material which provides a waterproof bedding for the glass in the frame. When putty is exposed to the air, it hardens during the first few weeks. If you need putty for metal frames, ask for metal-casement putty, as linseed oil putty does not bond to metal.

There is also a dual-purpose putty available which is suitable for both types of frames. Measure the dimensions of the frame in order to know how much putty to buy. Putty does not keep for very long before becoming too hard to use. Check the weight on the tub, but as a general rule, approximately:

1 foot length needs 4.5 ounces equivalent to 300mm length needs 125 grams 5 feet length needs 22.5 ounces equivalent to 1.5m length needs 625 grams

8 feet length needs 35 ounces (just over 2 lb) equivalent to 2.4m needs 1 kg

Mould the putty, by kneading a palm sized ball in your hands until it becomes pliable and does not contain any lumps. If the putty is too difficult to mould into shape, use a little linseed oil to soften. If, on the other hand, the putty is too sticky, wrap it in newspaper to remove some of the excess oil. It should be possible to roll it smoothly into long cylinders-sausages. Press the putty into the rebates all round, judging a sufficient thickness to bed the glass in, and spread to the edges of the rebate.

Self-adhesive plastic foam

Alternatively, instead of using bedding putty, there is a self-adhesive plastic foam available which can be used. This is applied all round the back of the rebate. Try to use it as a continuous strip, start applying at the top and take it all round the frame. Place the glass into position and press all round the edge, not in the centre of the pane. Check that there is a thin bed of putty between the glass and the inside of the frame. Secure the glass with sprigs before continuing with ordinary putty as with normal method.

Replacing the pane of glass

Press in the glass, by working with the fingers around the edges. Do not press at the centre of the glass. Remember that the point where it is bedded down on the putty will be visible, so try to get an even thickness behind it. Tap in sprigs in the case of a wooden frame or fit wire clips if the frame is metal. Space the sprigs along the edges approximately 20cm (8 inches) apart. The sprigs do not have to go in very far and may be tapped in by sliding the edge of a chisel or a light hammer across some card over the glass.

More putty can be added from the outside with the fingers, but it will have to be pressed in and smoothed with a putty knife. One with a diagonal cut across its end is suitable. Try to angle the putty outside, to an angle of approximately 45

Window Frames

Wood expands and contracts according to its moisture content and this depends on the weather for outside woodwork. Wooden window frames set in brick may develop gaps where water has entered and this causes rot. Do not fill these cracks with concrete, mortar or putty, as these set hard and do not allow movement.

Buy a mastic sealer from a builders’ merchant. This may come in a tube, so that you squeeze the sealer through its nozzle, or it may be in a gun with a lever action. Squeeze this into the gaps. If necessary, press further with a putty knife, which should be kept wet to prevent sticking. The mastic will set sufficiently hard to take the paint, but it remains elastic so that gaps will not form.

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