A method for assembling a rigid pipe intended to be placed in a body of water, the rigid pipe including a metallic inner tube, a thermally insulating insulation jacket formed from an assembly of insulating parts and an outer layer. The method includes the steps of providing the metallic inner tube, forming the insulation jacket, and forming the outer layer around the insulation jacket. The method includes a step for providing a plurality of helical insulating parts and a step of mounting the helical insulating parts around the inner tube in order to form the insulation jacket.