The Enquirer understands the victim was working on the top floor at Eastbourne Terrace where Wates is renovating the 18-storey office block.
It is understood that a pane of glass being moved into position on the roof came free and fell on the victim.
Wates said in a statement: “It is with regret that we can confirm that there was a fatality on site at 20 Eastbourne Terrace on Friday afternoon involving an operative from a subcontractor.
“Our thoughts are with the family at this extremely sad time.
“A full investigation has been launched and we are cooperating fully with the authorities to establish the circumstances surrounding this tragic incident.”
Wates started on site in June 2014 for client Land Securities with the project due for completion due next February.