Shattered double glazed window

Not long got in, and we found a double glazed window in an upstairs bedroom shattered - both panes shattered but still in place. Tempered glass but not AFAIK laminated.

There was apparently a loud bang outside last night (I’d nodded off) but we’re all pretty sure this window was ok this morning.

Very odd, weather has been dire recently but not particularly bad this morning though there was hail at some stage.

Somewhat baffled and concerned by this, perhaps just a bird?

Definitely a chore to fix we could do without currently.

Can’t access my ladders to cover the window externally at present, don’t really want to open it as it’ll probably collapse, tempted to stick some kind of sticky film over it but this again might just cause it to break and smash.

For both panes to smash implies a very significant pressure wave, like from a nearby explosion, or a point impact by something capable of penetrating through to the other pane - a projectile much tougher than your average bird. Any possibility of a gunshot? (Farmer killing pests?)

You could do worse than report it to the police, just in case - and scrtunise for any associated object below the window, or inside.


It’s very odd - we’re in the city so no farmers nearby. Something like an airgun pellet went through my mind, trouble is I can’t see a hole, at least not from the ground in the dark.

Both panes have shattered but not actually collapsed - I’d imagine some kind of issue due to contraction/expansion would only cause 1 pane to go, but maybe that’s enough to cause a big pressure change.

Might be tight tolerences in the sealed glass unit size in the frame, and changing temps causing contraction/expansion that pressed the sealed unit against the frame.

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At first it’s natural to think of logical reasons, explosion/impact, but sealed double glazing units do sometimes fail this way, the window is a sealed unit and stress cracks happen the rest follows quickly. It may be worth checking what thickness of glass was in the existing unit and increase this to minimise further problems.

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A few years back a peregrin falcon hit a pigeon in mid flight and flew straight into my living room window. There was a huge bang, a lot of pigeon feathers and a slightly stunned hawk but the window remained in tact. I’d be very surprised if a bird broke both sides of the window


Yes, could well be.

The windows were installed just over 3 years ago so a bit annoying and I suspect not covered by warranty.

We went for white aluminium frames for some reason and I think it was a bad idea - they get very cold in the winter, and I suspect may expand/contract more than uPVC would, from memory I think frames were thinner compared to equivalent uPVC window sizes.

Thanks, a bit of Googling did suggest such things are not uncommon, or that when fitting the sealed units occasional minor damage in the edges of the panels can be a source of future failure.

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I wondered about a bird as I’d seen some articles, possibly on the BBC, showing the imprints left on windows birds had flown into.

The loud bang Mrs AC heard last night is disconcerting, especially if the window was ok this morning - I hope it’s not a structural issue that stressed the window frame.

I’d think that this is the more likely explanation of both glass lites failing simultaneously. Although it’s possible that there may have been glass edge defects originating from the IGU assembly at the factory it’s not uncommon, especially in large commercial building projects for unauthorised adjustments to accommodate site dimensions/ tolerances to cause edge damage and stress points leading ultimately to glass fracture. Is the glass panel that failed an operable windows or a fixed panel and does the frame look distorted in any way (measured across the diagonals or any discernible twist)

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It’s a window that opens outwards, one of 3 in an outer frame - two opening panels below, one above.

No obvious frame distortion but will check again in good light tomorrow.

@Alley_Cat, you mentioned the window is approx 3 yrs old, my understanding is that the warranty for double glazed windows warranty should be in the region of 5-10 yrs, that’s where I would start. Of course this will depend and vary depending on how the contract was placed. Maybe worth a check with the supplier/installer initially.

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Yes, I need to find the warranty - I’m assuming perhaps that the cause cannot be definitely determined and would probably fail a warranty claim, but definitely worth asking.

I would take the attitude the window failed during normal use and that no damage/unauthorised use was attributable to yourself so the fault is either with the product and/or the installation. My view is the warranty should cover the replacement.
Good luck with the claim. The double glazing industry does have an ombudsman.

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That is good advice and rather than speculate on the cause of failure start the insurance claims process and write to the supplier notifying them of the incident. At the same time take a lot of really clear photographs of the window inside (and outside if the OP can) including photos of the glass breakage pattern. Also photograph the areas outside of the window confirming that there are no structural movement issues (cracks in the plaster internally or in the external brick bedding/perpend joints)

If the OP has a long straight edge/spirit level place it against each side of the window frame to see if there is any bowing.

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I suspect the bang was the sound of the window shattering and not something hitting it

Well interestingly, in daylight it seems only the inner pane has gone - the internal reflections between the panes must have simulated cracks on both sides with room/torch light - I did wonder from the outside last night when I looked with a brighter torch but it looked absolutely convinving from the inside.

That was my first thought to be honest, and concerning as it’s a child’s room - as the outer pane looks ok now it’s probably unlikely (which is reassuring).

Thousands of little cracks but they seem to radiate out from a point in the bottom left where cracks are further apart - there is no way there could have been an impact to that point because items on the windowsill obscured that region and would have been damaged/knocked over themselves in the process.

No pets to have done anything either, unless there was a tooled up house mouse trying to get out.

Possibly, though the bang was the night before - the lower half of the window was obscured by a sheet of synthetic material in front of the frame and not touching it with a poster in front - this is how I’m certain there had been no impact internally.

The odd thing is that 3 of us were in that room yesterday morning and the window was ok, at least above the poster/sheet - possible maybe that a small crack developed spontaneously the night before and worsened when we were out yesterday.

A friend of mine did that with his strimmmer…twice, his wife was not amused.

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