Well-made double glazing commonly lasts somewhere around 20 to 30 years, but the parts do not wear out together. The sealed glass units usually fail first, often showing as mist between the panes; hinges, locks and seals come next; the uPVC frame itself tends to outlast them all if it was fitted properly. That means a tired window can often be brought back with a new unit or new hardware rather than a full replacement.
Below is what shortens and lengthens that life, and how to tell which fix your windows actually need.
Which part fails first
The sealed unit
Each unit is two panes bonded to a spacer with a sealant. Years of sun, rain and temperature swings slowly break that seal down. Once moisture gets into the cavity it condenses on the inside faces and cannot be wiped away — the classic misted unit.
Hinges, locks and handles
Moving parts wear with use. Sashes can drop so they catch the frame, handles loosen and locking points stop lining up. These are usually individual repairs.
Gaskets and seals
Rubber gaskets harden and shrink over time, letting draughts and whistling in. They can often be replaced in the existing frame.
The frame
A good uPVC profile does not rot and resists weathering. Frames usually only need replacing when they are warped, cracked, badly discoloured, or were never fitted square.
What shortens the life of double glazing
- Poor original fitting — frames out of square put stress on units and hardware
- Blocked drainage slots — water sits in the frame and attacks the unit edge
- Exposed, windy sites — more movement and more driving rain
- Never oiling locks and hinges
- Harsh cleaning products or pressure washers on seals
Repair or replace?
If the frames are sound and square and the only problem is fogging, a new sealed unit is the sensible fix; that is what we mean by replace the pane, not the frame. Worn hinges and gaskets can be swapped too. Replacement makes more sense when frames are damaged, several windows have several faults, or you want a different style or better performance throughout.
We will tell you honestly which situation you are in after looking at the windows. The survey and quote are free.
Helping your windows last longer
Wipe frames with warm soapy water, keep the drainage slots at the bottom of the frame clear, and put a drop of light oil on hinges and locking points once or twice a year. Air rooms daily to keep indoor condensation down, and deal with a stiff handle early before it strains the gearbox.
Common questions
Not necessarily. Misting means the sealed unit has failed. If the frame is sound, replacing just the unit is usually enough.
Older or lower-quality profiles can discolour and become brittle. Better systems resist this well; we stock REHAU.
Yes. Individual sealed units are made to measure and fitted into the existing frame.
Call 07538 882579 or use the contact form to arrange a free survey.
Want a straight answer on your own windows or doors?
DM Installations fits and repairs windows and doors across Central Scotland — Cumbernauld, Glasgow, Falkirk, Stirling and the surrounding towns. Free survey, written quote, and an honest answer on whether you need a repair or a replacement.
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