For the production of a tight complex having an internal reinforcement or framework and more particularly intended for the production of aerostatic balloons, a nonwoven reinforcement (10) is formed from weft and warp threads arranged in the form of two superimposed layers. To each of the faces of said reinforcement and using a predetermined force is applied a covering film (16a,16b), after bringing it to its pasty melting point on a heating drum (30a,30b). The nonwoven character of the reinforcement makes it possible to preserve the seal of the covering films during complexing. Moreover, the formation of small loops or rings on the edges of the complex obtained in this way makes it possible to introduce connecting cables facilitating the taking up or absorption of stresses.