Window sashes are the frames that contain the window glass and can be fixed or operating. In a single hung vertical window for example, the top sash is fixed or not moveable.
The lower sash hangs from sash cords or spring balances and operates, or moves up and down. Sashes can be repaired if they are in otherwise good condition.
The most common thing that breaks in a window are the sash balances. All of a sudden, an old window becomes hard to lift because one or both of the cords that attach to the balance weights have broken.
Modern windows use sash balances too, but they are usually long torsion springs installed on both sides of the window attached to the moving sash. These springs are quite flimsy and they break more frequently than old windows with lead weights and sash cord.
A lot of the time the plastic pivot block that connects the spring to the bottom of the moving sash gets old and brittle and cracks or shatters. You will often see a long spiral metal spring hanging down past the bottom of the moveable window when this happens.
Replacing sash balances is usually not that difficult, The trick is getting the exact same length as the old and getting the right weight. Sash balances have different colour markings for different weights of windows. Green for light weiight, Blue for Medium and Red for heavy duty.The colour is usually a painted band or a plastic ring on the sash balance.
Pivot blocks are another problem. If these break it might not be possible to replace them .especially if the window manufacturer is out of business. Its sometimes necessary to cut the window frames to get the old pivot blocks out.
Wooden sashes can have glazing that is held in by glazing points and putty. The glass can also be held in by thin wooden mouldings. If the glass is broken, the mouldings can be removed by carefully cutting through the dividing line between the sash and moulding with a utility knife. Then gently prying the moulding off, hopefully in one piece.
More modern vinyl sashes can also be repairable. In a vinyl sash the glazing is usually held in with thin vinyl glazing strips accessible from the inside. There are a few questionable designs where the vinyl window sash is glued around the glazing and you basically have to replace the entire sash if the glass gets broken.
Most vinyl sashes though do allow glass replacement by just gently prying out the glazing strips. Unlike wooden sashes, vinyl strips are not as prone to breaking and the glass generally requires no putty so reglazing is relatively easy.
Aluminum windows use a similar arrangement as vinyl to hold in the glazing. Except the vinyl strip is usually made of a much softer vinyl which simply clips into a groove all around the inside of the sash.
Unlike a vinyl window, the glass in an aluminum sash is held in with a very soft sticky butyl rubber compound that comes in the form of tape. You have to cut through the butyl rubber all around the the glass with a thin knife blade to get the glass to come out.
Or, in the case of large aluminum windows, you use a pair of suction cups to progressively pull the glazing off the sticky rubber. To reglaze you need to clean all the old rubber from the frame and apply new glazing tape all around the frame.
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