This paper deals with the gridshells built by the Navier laboratory in the last ten years. The numerical conception is developed, from the draft made by architects up to the final structure. Several numerical tasks are performed to design a gridshell. The geometry of the gridshell is first considered. Then, an important iterative step mixing geometry and mechanical considerations is carried out. In particular, it is explained how the naturally straight beams are bent together during a very quick step leading to the final shape. Thanks to this active bending, double-curvature shapes are made and offer many interests like high stiffness for a light weight structure. Lastly, the geometry of the membrane is drawn based on the numerical final geometry of the gridshell. The improvements of gridshells, including safety considerations as well as practical considerations are also developed, through the four gridshells recently built. Finally the model is improved to take into account the torsion which can have an important effect, especially when the beams have a rectangular cross section.