A method for controlling the thickness of a continuous elongated element made of elastomeric material, applied according to coils wound on a forming support, includes: advancing a head end of the continuous elongated element toward the forming support; subjecting, during the advancement, the continuous elongated element to a first stretching with a first stretch coefficient before applying on the forming support; and subjecting, during the advancement, the continuous elongated element to a second stretching with a second stretch coefficient during the application on the forming support. During the first stretching, a span of the continuous elongated element adjacent to the head end is stretched with a supplementary stretch coefficient greater than the first stretch coefficient, in a manner so as to confer, also to the span adjacent to the head end, a stretch and a section similar or substantially equivalent to those of the rest of the continuous elongated element.