Windows may crack or stick, the frames warp or let in water and sash cords break. These common faults in windows are relatively easy to correct and it is worth doing so at the earliest possible stage to avoid prolonged inconvenience or further damage. But make sure any repairs are done thoroughly or the problem is likely to reoccur.


Sash windows are commonly found in older houses and the sash cords on which the windows hang are likely to wear and break with age. Replacing sash cords has been covered in detail earlier in the Course, but there are several points which you should bear in mind. You will have to lever out the beads on either side of the window inside the room and it is important to keep the wood intact; start at the centre point of each bead to avoid damaging the mitre joints at the top and bottom. You should replace all cords even if only one is broken. For replacement use tcrylene cord since this is much more durable than the old-fashioned wax type. You can prevent the cord fraying by heating the end with a lighted match to melt the fibres into a solid lump.


There are various reasons why sliding sashes and hinged casement windows in both timber and metal start to stick. In some cases new paint may have gummed up the window. Cutting round the opening faces with a sharp trimming knife will usually alleviate the problem, but sometimes you may have to force the faces apart by inserting the blade of a broad filling knife between them. If the trouble is caused by a gradual build-up of paint over the years, use paint stripper to get back to the bare wood or metal; alternatively use a blowtorch to remove the paint from the wood. Make sure there is adequate clearance between the fixed and moving parts of the frame – in most cases 1.5mm clearance is sufficient – and repaint.

Poor paintwork and cracked glass can allow damp to get at the frame causing wood to swell and metal frames to rust. Use a wire brush to get rid of rust, treat the frame with rust killer and apply metal primer, undercoat and gloss paint. With a swollen timber frame it is best to strip off the paint with a blowtorch, taking care not to damage the glass, and gently play the blowtorch flame over the inside timber to dry it out. In hot weather you can leave the frame unpainted for a few days; this will help to get rid of damp. When the wood is dry, rub it down with glasspaper or use a plane to give a 1.5mm clearance round the frame. Make sure the putty is sound and, after priming any areas of bare wood, cover the frame with at least three coats of paint to ensure the timber is sealed against damp. Remember to take about 3mm of paint onto the glass to form a seal between the glass and the putty and prevent water seeping down into the frame.

Sash windows which stick may often be freed by opening the sash to its fullest extent and sanding the channel with coarse glasspaper wrapped round a block of wood. Where the trouble has been brought about by paint building up in the channel, you may find it necessary to strip the surface back to bare wood and repaint. If the wood has swollen, you should take the sash out of its channel and plane it on each side where the sash cord is fixed.

With hinged timber windows, sticking may be caused by incorrectly fitted hinges. If the window is binding hard up against the side where the catch is fitted and there is a gap on the hinge side, the hinge flaps should be sunk deeper into the wood. On the other hand, if the window is binding hard up to the frame on the hinge side while there is a gap on the catch side, pack thin pieces of card under the hinge flaps to prevent the window sticking.


The opening frames of casement and vent windows often become warped and ill-fitting. It is usually possible to compensate for the warp and eliminate or minimize the gap by adjusting the position of the hinges. If the gap is not completely closed, you can seal a timber window with a suitably shaped timber strip; fix it with panel pins, at about 50mm intervals, into the rebate of the fixed frame. Alternatively, for both timber and metal windows use a flexible silicone rubber gap filler. Make sure the gap is thoroughly clean and dry; then apply self-adhesive masking tape to the inside face of the opening frame to prevent the filler adhering in this area. Squeeze the filler out of its tube into the gap and leave it to set overnight; the window can then be opened and the tape removed.


Never try to force an ill-fitting frame back into the right position since the glass is likely to break under the strain.


Damp patches on a wall around a window may indicate an external gap between the brickwork and the frame. To seal the gap, use a bead of non-hardening flexible mastic, applying it with AN applicator which injects the mastic through a plastic nozzle.

Check the frame has drip grooves incorporated to prevent rainwater being drawn between the opening and fixed parts of the frame and make sure the grooves have not been filled with layers of paint. If necessary, scrape them out and repaint. Modern casement windows are designed with overhanging lips as well as drip grooves to prevent water ingress. Old casements may not have this lip; if they are letting in water, it is a good idea to screw hardwood weatherstrips along the bottom of the opening casements and top vents. If French doors are letting in water, screw weatherboards to the bottom of the doors to throw water clear of the sill. In both cases use rustproof screws at approximately 100mm intervals.


Replacing glass in ordinary windows has been covered earlier in the Course; replacing individual panes in leaded light windows, however, requires different treatment. The panes are held in H-section strips of lead, called cames. To release a broken pane, cut the cames at each corner with a sharp knife and lever up the lead flanges at the sides and bottom with a wide chisel.

Either use the old pane as a template to cut a new pane or make a card template to fit in the cames and cut a new piece of glass about 1mm smaller than the template.

Traditionally gold size putty, obtainable from builders’ merchants, is used to bed the glass in the cames; but you can bed the glass on a thin strip of grey mastic. Insert the new glass under the top flange and then carefully fit it at the sides and bottom; use a wood stick to press down the edges of the cames. Clean lead with medium glasspaper; resolder each corner with soft, resin-cored solder applied with a hot soldering iron. Leaks If a leaded light leaks, scrape dirt away from the flanges of the cames and brush under the edges with clear polyurethane varnish. Make sure the flanges are well pressed down and use a razor blade to clear away varnish from the glass after it has set. If this does not stop the leaks, you should cut the came corners and use a chisel to fold back the lead in the affected areas so you can fit a thin strip of mastic or gold size putty under the flange; this will seal off the pane completely.

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