Building structure for greening top surface of building

The utility model discloses a building structure for greening the top surface of a building. The building structure comprises a roof layer made of reinforced concrete, wherein the roof layer is provided with a waterproof layer which is provided with a waterproof protecting layer; a root separating layer is arranged on the waterproof protecting layer and is provided with a water storage layer which is provided with a water permeating and discharging layer; and the water permeating and discharging layer is provided with a soil separating layer which is provided with a soil layer. The building structure disclosed by the utility model has the advantages that the root separating layer is arranged on the waterproof protecting layer, can block the root of a plant from entering a top-layer structure of the building, and is provided with the water storage layer, the water permeating and discharging layer and the soil layer in sequence so as to provide a good growing environment for the plant; the water storage layer is paved with gravels or pebbles with the particle size of 1.5-4cm so as to form the water discharging layer, and residual rainwater falls quickly through gaps among the gravels or the pebbles and is discharged by a water discharging system; and foamed plastics with the thickness of 4-8cm is adopted for paving on the root separating layer to form the water storage layer so as to provide necessary water for the plant.