A patented self-tensioning system for long-span wooden structural floors is described that increases the performance of the deflected sections in terms of both resistance and deformation. The system is based on a force multiplier mechanism composed by two connecting rods which are secured to a post-stressing tendon. The mechanical device is activated by the transmission of the load from the structural element to the supports, causing an elongation and stressing the tendon. This transmission comes with a slight vertical displacement of the supports. Throughout this system, the intensity of the tensioning force varies with the applied load; thus, a more favorable bending moment distribution from the load is obtained, and the relative deformations of the different sections of the piece are reduced. This article presents a comparative study of the structural behavior of p-shape cross section wooden structural floors with spans from 9 m to 18 m, comparing sections with and without pre-stress, and sections with the self-tensioning system.