Over the passed few months, I have been having major work carried out on my own house, complete with scaffolding, a few weeks back the scaffolding was removed, and I was ased by my wife to clean our windows after months of neglect,
I went out and started to clean the windows using loads of water, Applicator, blade and scraper (unger) while I was washing the windows I noticed quite a few scratches some in clusters and some single, when I pointed this out to my wife, she then told me, were one piticular scratch was and it was a cluster typ scratch, she then told me she remembered a part brick falling and hitting the window, I myself remember small amounts of bricks and rubble falling and hitting the windows, and this has caused scratches to the windows.
I called the builder over and showed him all the glass scratches, He tried to fob me off with all sorts of cra*p, and even said it must have been the way I cleaned the windows, It was then I pointed out to him that I was a professional window cleaner, and knew how to clean windows, especially builders cleans, after a few arguments with the guy and with a threat of me taking him to court, he agreed to replace my glass, this has since been done.
Don't take any cr*p from these people and threaten to counter claim if they can't sort out the problem, I knew there were no scratches in the glass but didn't have to prove it, if they have been doing any major renevations to the property you have cleaned, then the chance's are they caused the damage.