A method for producing preforms, by layup of fibers on a layup surface, comprising the application of a binder on at least one continuous flat dry fiber, comprising two opposite main faces, and the layup of the fiber provided with binder by means of a layup head in order to form a preform. The application of binder on a fiber is carried out by means of at least one fiberizing nozzle comprising a discharge orifice supplied with liquid or pasty binder, and one or several injection orifices supplied with pressurized gas, in such a way that said nozzle is able to deliver the binder in the form of a spiral filament, the spirals of filament being deposited on a first main face of the fiber running underneath the nozzle in order to obtain a fiber provided with filaments of binder.