The acceleration in electromagnetic railguns of projectiles with a mass of several hundreds of grams up to velocities ranging between 2000 m/s and 3000 m/s requires currents with intensities of several MA.In the ISL rail launchers the repulsion forces created by these currents acting on the rails of the launcher can reach values in the order of 20 MN/m. The housing of the launcher has to withstand these high mechanical stresses to maintain the rails in position and thus to keep the caliber constant. In this paper a comparative study of different possibilities of housings is presented. The limits of the actual fiber wound materials are shown and a selection of new insulating materials capable of withstanding the mechanical stresses is given.We also present the concept of a housing made of insulated steel plates allowing a good mechanical stiffness combined with a minimum loss due to eddy currents in steel. In particular, we show that the good mechanical behavior of the steel plate housing makes it possible to reach the same overall efficiency as that obtained with a fiber-wound material housing.