[Dave Willis]

Cleaning this window and it got me thinking - "I wonder where the water goes?"

[Dave Willis]

............. so I asked the lady of the house "I dunno lets have a look" so inside we went and there it was all over the bathroom floor 

I wonder if the window is fitted inside out 

[PoleKing]

Yup. Fitted inside out.
Deliberate? I doubt it.
Probably fitted by the apprentice.

[Simon Mess]

Year before last, one of my customers had a large extension built on her house which resulted in my just doing the front for 2 or 3 months. 1st time i did it after it was finished, i was about to remove a sticker from the new bathroom window when i noticed what it said. I went to get the lady and showed her, it said:

                                                    THIS SIDE OF GLASS MUST BE ON THE INSIDE

                                                                         

[Neil Gornall]

I once did 30 builders cleans on a new estate in Spalding.

50% of the glass was fitted the wrong way round. The site foreman said "just take the stickers off and no one will know"   

I did it then, but would tell him to shove it now!

[Ste M]

I cleaned a big conny roof in and out, the lady warned me before hand that the self cleaning roof was now inside haha, they had fitted all the glass upside down, the conny cost 28k and surprisingly the company was bust but had opened back up in the same place with the same staff but a different name an different owner

[Ian Lancaster]

A fairly common one is frosted (or patterned) double glazed units.  These should comprise an inside sheet of plain glass and the outside of frosted, with the actual frosting on the inner surface, so presenting a smooth surface to the outside.

Many times I've come across units where the frosting is on the outside, making them 'dirt traps'.