Abstract: The object of the invention is a multichamber structural element manufacturing method which for forming a multichamber structural element with chamber profiles (1) extending radially from the center defined by the connection of the chamber profiles (1) comprises the following steps: at least three chamber profile preforms (2) are provided, wherein each chamber profile preform (2) comprises two walls (3) made of a sheet of metal material and arranged with respect to each other in substantially parallel planes with a gap retained between them, wherein the edges of the individual walls (3) converge, and wherein a valve element (6) is arranged on at least one wall (3); the unconnected wall (3) edges of each of the chamber profile preforms (2) are sealed with a seal (5) for forming a closed hermetic empty inner space of the chamber profile preform (2); a fluid under pressure is introduced through the valve element (6) into the inner space of the chamber profile preform (2) for forming a deformed chamber profile (1

Abstract: The object of the invention is an 1-profile preform which comprises an outer wall (1) of the first flange and two inner walls (2) of the first flange arranged with respect to the outer wall (1) of the first flange, a first web wall (3) and a second web wall (4) being arranged in a plane parallel with respect to the first web wall (3), an outer wall (5) of the second flange, and two inner walls (6) of the second flange arranged with respect to the outer wall (5) of the second flange, wherein the corresponding walls (1, 2, 3, 4, 5, 6) are arranged with respect to each other while retaining a gap forming a closed empty inner space of an 1-profile preform, and wherein a valve element (7) is arranged on at least one wall (1, 2, 3, 4, 5, 6). The object of the invention is also an 1-profile manufacturing method with the use of an 1-profile preform.