Abstract: A method for making floors for filters, particularly for filters including a granular filtrating material, wherein the method includes forming two stages. The first stage is made by casting in concrete or the equivalent, at least one carrier self-supporting element or pre-slab, formed with openings in which are housed elements, such as nozzles, for the introduction of fluids used for washing the filter. Then the second stage is formed, during which, once the carrier self-supporting elements have been put in position on the supports of the filter, concrete is cast in a single operation on this element or elements, in a quantity sufficient for reaching the required total thickness of the floor and thereby providing a slab which will receive the filter granular material.