The formation of silica films via sol–gel route on disordered mesoporous and macroporous supports is reported. These films are structurally characterised by TEM, XRD, XPS and permporometry. It has been found that the ordered mesoporous silica layer does not grow directly on a mesoporous support. Instead it grows on a structurally disordered interface of 10–20 nm thickness. This observation differs considerably from studies on film formation on dense supports as reported in the literature. Water transport experiments were carried out on the silica films deposited on porous supports. The results suggest that the disordered interface layer of the film deposited on the mesoporous support does not contribute significantly to the total resistance for water transport.