When the glass is the problem, not the window
Four failures account for most of the glass replacement we do:
Cracked or chipped panes. A safety issue as much as a cosmetic one, particularly at low level or where children are around. Left alone, a crack propagates.
Fogged sealed units. Condensation between the panes means the perimeter seal has failed. It cannot be cleaned, dried or repaired — the unit is replaced. The frame is almost always fine.
Etched or scratched glass. Years of monsoon grit and cleaning leave the surface hazy. It looks like dirt, but it is physical damage to the glass.
Single glazing that is simply not enough. Not a failure at all — just a window that was specified for a different era, in a room that is now too hot or too loud.
What the frame has to be able to take
This is the check that decides whether glass replacement is possible at all.
A single pane might be 4–6 mm. A double-glazed unit is typically 20–28 mm overall and several times the weight. That has consequences:
- Rebate depth — the frame needs a deep enough channel to hold the unit and its gaskets
- Bead and gasket type — a unit needs continuous support and a drained, ventilated rebate, which older frames often do not have
- Hinge and hardware capacity — an opening sash carrying a much heavier unit will drop if the hinges were sized for single glass
- Frame stiffness — a slender old section may flex under the extra weight
We check all four at survey. Where the frame will not take it, secondary glazing or acoustic inserts get you most of the way without replacing anything.
Choosing the replacement glass
Safety and security
Laminated glass bonds a polymer interlayer between panes so fragments stay in place when it breaks. Toughened glass is several times stronger and breaks into blunt granules. Laminated is the better choice for security and at height; toughened for impact safety in large or low-level panes.
Thermal comfort
Double-glazed sealed units slow heat transfer. Adding a low-E or solar-control coating reduces the heat that comes in through a west-facing window without making the room dark.
Noise
Acoustic units use two panes of deliberately different thickness with a laminated inner pane. Two identical panes resonate together at frequencies traffic noise is full of; making them different breaks that.
Privacy and light
Frosted, tinted, reflective and patterned glass all trade transparency for privacy in different ways. See glass options for what is available.
What the visit involves
- Survey and measure the aperture, and check the frame can carry the new unit
- Manufacture the pane or sealed unit to size
- Remove the old glass and dispose of it safely
- Bed and bead the new unit, with the rebate drained and ventilated correctly
- Adjust hinges and hardware for the new weight
Safe removal and disposal of broken glass is part of the job, not an extra — which in an occupied flat matters more than it sounds.
If the frame has failed too
Then this is the wrong page. Window replacement covers the whole unit, and window frame repair covers frames that can be restored. Send a photo of the frame and the sill with your enquiry and we will tell you which of the three you need.