Came down to find the glass in the back door broken ....

choille

Surface tension OH reckons. There was a time a while back where new PVC units that were outlawed in Europe because they didn't meet the EU Standards were getting sold here on the cheap, but that was pre 2005.

hazyjo

Double check for any movement on the walls (cracks, etc) or if drains have sunk at all (if present)... although from the sound of it, it's fairly common and probably doesn't mean there's been any movement in/under your utility room.

Jx

dizziblonde

I know of a couple of schools that have installed double glazing relatively recently where one of the plates of glass has spontaneously begun to crack, but it's been a crack that's run up the pane gradually so to speak and not as dramatic as you describe.

MrsAtobe

One of my sister's double glazed doors went after being hit by an acorn. Yes, I'm serious! Her youngest was running past the door, her foot connected with the acorn, which then hit the door. The noise was incredible - I was there at the time.