No warranty on 10m old double glazed window?

We had double-glazed windows put in throughout our house earlier this year.
The products are good, fitting worked well, cheerful tradies, reasonable price.
But now one of the windows has developed a crack about 40 cm long about 2 m from the floor. The company we bought the windows from sent an inspector this morning to look at the job. He determined that it was a “thermal crack”.
He explained that there was no warranty for this type of crack because the company that supplies glass to the window company won’t provide a warranty.
I don’t recall being told that there was no warranty for glass that cracks in this way. There is no mention of warranties on their website.

Is the window company still liable in a case like this - under Australian Consumer Law?


Any written warranty is in addition to the ACL, so you still have rights under the ACL. You could claim various ways but since they stated ‘it is thermal, no warranty’ keep it in writing and formal from here on, citing chapter and verse of your rights, your claims, what you want, and by when they need to respond (2 weeks is usually considered reasonable).

It could be through claiming issues surrounding merchantability/quality or other aspects to seek service. Regardless, you will need to include evidence supporting your assertions. If they stonewall or reject your claim unfortunately your next stop would have to be at your state xCAT (tribunal) regarding your rights under the ACL and their response. Even then if they choose not to adhere to any xCAT ruling against them, you might need to go to a court for papers requiring them to do so.

It seems thermal issues would be common across much of Australia, so fitness for purpose might be something to read on as supporting evidence.

Good luck and let us know how you go.


Thermal cracks are caused by differential heating of the glass in the window or the window surrounds, causing stresses which lead to cracking. The cracking isn’t necessarily (it is unlikely to be) caused by a defect in in the window, but the window’s location.

It is possible that the house itself or the location of the window in the house cause the failure, rather than the window itself.

Possibly not as the product possibly isn’t defective, but the window’s location/stresses within the house caused the crack.

As the ‘house’ or ‘window location within the house’ has been assessed as the likely cause of the failure, see if your house insurance covers such damage.

Think it a bit like a stone hitting a windscreen of a car. The cracked windscreen isn’t due to a fault in the windscreen (a fault would fall under the Australian Consumer Guarantee), but the stresses caused by the stone hitting the windscreen. The cracked windscreen becomes a insurance claim rather than a claim against the car manufacturer for a defective windscreen.

The only way to prove that the window cracked because of a fault is to get an expert to assess the window and how it was made/installed. Such would be a very expensive exercise (possibly $1000s) and may not come with a dissimilar conclusion to that of the ‘inspector’ already sent. The expert would also need to rule out things like building movement or accidental damage (bird strike/stone from mowing etc) which can also cause window glass to crack.


Thank you!


If a stone hit the window or if the windshield on the car spontaneously cracked in the heat without having been damaged/hit by a stone it would be similar.

Since he stated it was a thermal crack I would opine while the cracking isn’t necessarily caused by a defect, the leap from that to it is unlikely to be caused by a defect accepting it may be unlikely, but based on what has been posted, a second opinion from ‘not the installing company’ might be warranted.

Thermal cracks happen, and in stronger objects than a window.


but assuming it was the house or the location of the window or the aspect would discount whether the window supplied was fit for purpose. A spontaneous thermal crack might be expected up north, in the centre, but less so in much of Tassie or cloud covered Melbourne.

If I purchased a window in NE Melbourne that had a spontaneous thermal crack I would question its quality. If the same thing happened in suburban Coober Pedy I would be more inclined to agree ‘stuff happens’.


From your OP the supplier was responsible for the supply and installation of double glazed Windows. The supplier was also responsible for the fit up.

How long would a pane of window glass be expected to last in an Australian home, assuming it is defect free and fitted correctly? Longer than 10 months based on our experience across a number of the newly constructed homes we’ve lived in over the previous 30 years.

If a pane has cracked it’s worth considering the pane is either poorly fitted or the pane had a microscopic manufacturing defect. Thermal cycling will cause either situations to initiate a crack. Do Windows in Australian homes experience thermal cycling? Of course they do. If any of the Windows double glazed had an unsuitable aspect, it would be up to the supplier who has been paid by the home owner to say so when quoting the job.

Is the window glass pane which cracked of merchandisable quality? My BS meter re the inspectors cause is wavering. It may be due to thermal effects. But only if the supplied material had either been installed incorrectly, or contains a manufacturing defect. Only a half truth from the inspector.

Food for further thought. The warranty of one major Australian glazed products manufacturer and supplier.

10 years!


A further point to consider from a glass manufacturer. There is an assumption here that the glass the OP noted as failed has a crack that extends from the edge of the pane.

Noteworthy is the discussion of low and high energy thermal failures. High energy failures are noted as rare, and occur under conditions that a site survey can identify prior to installation. Higher strength glass is one recommended response. Low energy failures are the more common and relate to edge defects arising either during manufacture or in handling and installation in the frames.

The possible failure of glass due to thermal conditions is a very specific and technical condition. A risk the average consumer would reasonably have little knowledge of.

In respect of warranties, similar to insurance, if it’s not a written exclusion, should the purchaser/consumer be expected to cover the risk?

A further resource may be the Australian Glass & Window Association.
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