It comprises a series of vertical profiles (1, 20, 21) anchored to cogged brackets (3) and previously fixed to the slabs or resistant structure of the building. It also comprises horizontal profiles (15) which are fastened to said vertical profiles and to which retention clamps (27, 28, 29, 32, 33) are connected in the flagstones (24), which have grooves on their horizontal edges.The vertical profile (1, 20, 21) has a frontal “C” rail (18) which is fixed to one of the U-shaped parts (16) that interconnect with other parts (17) mounted on a C-rail (19) of the horizontal profile (15).The horizontal profile (15) includes frontal upwards flanges (25, 26) for anchoring clamps (27, 28, 29, 32, 33) with flanges (31) to be inserted in the grooving of the flagstones (24).