It doesn't get any worse than that account Fred - although I would suggest that, that example perhaps, is just the tip of the iceberg when considering how much alteration works are carried out by those somewhat 'uninformed' companies in order to save a shilling or two?
As noted to our friend Dannyboy, if in any doubt at all, get the experts involved, otherwise don't just assume that it's ok and, never expose your operatives to any risk situation.
Regards
MVM