we’ve just come back from a weekend away to find the interior pane in my lad’s room has a two foot hook shaped crack in it. I’ve duck taped it up like something from the war and will be on to the builder tomorrow,  but what’s done that?

they’ve only been in 6 months

but what’s done that?

Did your lad have an empty whilst you were on a weekend away?

Our single glazed window on our summer house did similar a couple of weeks back. Toughened glass though so the whole thing just crazed.

Had the same happen only the inside pane was in small pieces. That window was probably around 10 years old at the time. Glazier who put a new unit in said he’d done quite a few very recently and said it tended to happen with rapid temperature changes.

We all crack under pressure! Even glass.

The sealed unit has possibly been packed in a bit too tightly or a flaw in the cut edge of that piece of glass, temperature changes can do that. Is it cracked from a corner?

Get the supplier / installer back to replace the sealed unit.

Think it must be the heat. A window has cracked (crazed in their case) due to the heat earlier this week. They were sat in their kitchen, hears a crack and the window had gone. Not sure how the heat had done it…..must be a thermal fight between the frame, double glazed unit and the window aperture maybe.

Possibly a nicked edge in installation but also possibly nickel sulphide inclusion (google it). It happens, rarely, but happens.

my lad’s 5. He was with us.

The ghost of Ted Moult drumming up business ?

customer had this a few weeks ago on a internal panel on a conservatory, toughened glass and a big mess, external panel ok

We’ve had 6 internal panes go in various parts of the curtain wall system at work. Only 1 could be atributed to impact (and that was a tiny milk jug!) over the last 4 years. It’s south facing gets really hot when the sun’s out.

A Toughened gass panel in the banister on the main stars shattered into smithereens for no reason at 0750 three Sunday mornings ago (watched it go bang on the cctv) and the van windscreen had a J shaped crack the other day. No explanation other than the heat

The majority of them have happened when the building has been empty and locked up.

Thermal stress is the most likely cause, particularly if it’s a large pane. Were the blinds or curtains closed?

@Phil_H your issues sound like they could be due to nickel sulphide inclusions within the glazed panel. Very small pockets of gas within the glass which are affected by changes in temperature and the cracks propagate .

Toughened glass should go through a rigorous quality control check before it reaches the end user,  however there is still a risk that imperfections could be present in a pane that has passed through this QC.

Most commercial /public facing toughened glass is also laminated, so if it fails due to inclusions then the pane often slumps within the frame and doesn’t fall out.

As for the OP,  probably related to the recent sun and high temperatures . Possibly movement in the building due to the ground drying out. Putting stress on the frame.

My office many years ago was located in an old part of the building adjoining a newer built section. It had a single pain of glass that developed a crack due to building movements. I took to marking the progression of the crack over several months with a permanent marker until I got the hell out and found a better job. Key point: hot weather can sometimes cause building movements that produce cracks.

Had it in the past. Normally the window was older and had started to mist so I assumed it was thermal/fluid expansion.

by older I am thinking 10-15 years

You didn’t have a black out blind on it by any chance? We’ve made that mistake on a south facing window and it went on the inside pane.  No idea if it was the cause but could well be.