We demonstrate a low cost and efficient method to engineer deterministically a defect between two well-ordered silica opals by sputtering silica on the top of the first one. The optical response of these sandwich structures is studied in terms of specular reflection and transmission spectroscopy. For a given thickness of sputtered silica, tailored highly transmitted and reflected optical modes are evidenced. The very good agreement between the experimental results and the simulations, run without fitting parameters, demonstrates the good control of the geometry of our structures. The macroscopic realization of well-controlled 3D photonic crystals with planar defects, presented in this paper, opens the way for an efficient manipulation of embedded nano-emitter fluorescence with applications in the fields of light-emitting devices and high- sensitivity pollutant optical detection.