Here, a novel approach for smart structures with piezoresistive coating based on graphene nanoplatelets (GNP) is investigated which are directly sprayed onto surfaces. The investigation focuses on flexible, durable and well adherent GNP coatings without changing the properties of the structure due to its inherent thinness and lightness. The sensitive coating provides the detection of external stimuli in the form of strain. In comparison to commercial strain gauges the GNP coating shows higher sensitivity. The validation on a frame structure shows the enhanced sensitivity with graphene nanoplatelets monitored by non-destructive evaluation methods. A detailed simulation model of the GNP coating helps the understanding of the underlying sensing mechanism. Cross-sensitivity towards undesired environmental influences such as humidity can be reduced by encapsulation. The novel coating promises an innovative approach for sensor application of graphene nanomaterials in the field of smart structures.