Flue for building construction

The utility model relates to a flue for building construction, mainly aiming at solving the problems that the existing flue of a building is easy to be subjected to indoor smoke returning and outdoor cold air flowing backward. The flue for building construction is characterized in that a family splitting flue (7) is provided with a unidirectional air door (8) which is open toward one side of a common flue (1); the family splitting flue (7) is internally provided with an axial flow fan (4); the side wall of the family splitting flue (7) is fixedly provided with a gas sensor (2) and a temperature sensor (3); the axial flow fan (4) is connected with a smoke exhaust ventilator (6), the gas sensor (2) and the temperature sensor (3) through wires. The flue exhausts smoke thoroughly, and can prevent the phenomena of smoke returning and outdoor cold air flowing backward.