In this communication, we present a design methodology for an insensitive radiating structure for concrete health monitoring applications. It takes advantage of an optimized smaller vacuum box surrounding a patch antenna. The Ansys HFSS software is used to simulate the studies of different configurations. The patch antenna consists of a radiating metallic element with a ground plane printed on a low-cost FR4 substrate. It is optimized to be linearly polarized and to be able to operate in free space medium at the first two resonant frequencies of 1.55 GHz and 1.95 GHz. This study demonstrates that a 5 mm high vacuum box above main radiating antenna, is sufficient to reduce the influence of three surrounding dielectric materials studied in this work, such as a PVC, concrete and limestone. Theoretical predictions, for all types of surrounded materials, show reasonably good agreement with experimental results.