The existing glass of this penthouse flat in Bath had broken as a result of Nickel Sulphide Inclusion. Nickel Sulphide Inclusion is a rare, but naturally occurring phenomenon in glass. Impurities can still be contained in the glass pane after its manufacture and toughening processes. Invisible particles of Nickel Sulphide can still be present and at any time they cause the glass to spontaneous break.
Normally, the building uses heavy cranes to lift the glass over the top of the building. We used a trolley crane internally and spider MEWP (Mobile Elevated Work Platform) externally, with a team of 4. A heavy crane would normally require at least a team of 8 and takes a lot more planning.