Building with excellent location in Oeiras and views of the Tagus River, for high-rise construction. Characterization of the urban planning operation: alteration and expansion of a collective housing building Alteration and expansion of the existing building, maintaining the predominantly residential use, complemented by a commercial fraction on the 1st floor. Due to its aesthetic and heritage value, the intention is to maintain the main facade, but remodel the entire remaining part of the building, through alteration and/or demolition and (re)construction works. Given that the gable roof coverage is an integral part of the image of the existing building that is intended to be preserved and has visibility from the urban area to the north, the alteration and expansion project envisages its reconstruction, with adjustment of the slopes to enable the addition of a fourth floor on this front, integrated into the roof attic. To the rear, a volume with a different exterior character from the existing one will be added, with five floors, implementing the expansion by two floors above the threshold level in relation to the existing construction and covering, on that front, the gables of the adjacent buildings. The proposed operation proposes an equal expansion below the threshold level, with the creation of two floors for parking light vehicles. Area chart Initial plot area: 310.57 m 2 Area assigned to the public domain: 23.36 m 2 Private area (after transfer): 287.3 m 2 Implementation area: 287.31 m 2 Total construction area: 1,348.48 m 2 Building area: 796.27 m 2 Construction index: 4.69 Waterproofing index: 1.00 Number of floors above threshold: 5 Number of floors below the threshold: 2