Cairo faces many problems such as overpopulation and environmental pollution due to the lack of green spaces in it, with the lack of empty spaces suitable for cultivation. In view of the large spread of the existing residential buildings in central Cairo, a study was conducted on the feasibility of greening the existing roofs of residential buildings with one unity to retrofit the roofs of these buildings and make use of them from an environmental, economic and architectural point of view. El Obour residential buildings were chosen as an example of a populated group of buildings under the one association of the Union of Owners in order to ease the application of roof greening to them. In case of working on existing buildings, the type used in roof greening must be studied in terms of loads and the appropriate installation method for these roofs.