A membrane applicator comprises a wheeled carriage adapted to ride on a surface to be covered with the membrane. A roll mount system is provided on the carriage to support a roll of membrane thereon. A press roll is mounted to the carriage for pressing the membrane against the surface to be covered as the membrane is being unrolled from said roll mount system as a result of a displacement of the carriage on the surface. The applicator is particularly well suited for applying bituminous membrane on flat roof surfaces of commercial and industrial buildings.