Abstract: A prefabricated balcony unit including a platform, safety rails, and attachment means.Renovation of balconies in old buildings is a complicated operation, in addition to being time-consuming and costly. The balcony unit in accordance with the invention has for its purpose to eliminate these drawbacks. The platform is in the shape of a coffer which is open towards the wall to which the balcony unit is to be anchored, said coffer arranged to enclose the free surfaces of the existing but damaged concrete platform of the original balcony. The balcony unit is also provided with attachment means designed to anchor the balcony unit to the building and dimensioned jointly to take normal loads on the balcony with the prescribed safety margin and preferably also the dead load of the concrete platform of the original balcony.