This case study shows how rebar mapping supports structural rehabilitation in aging buildings. A 60-year-old Mumbai building, lacking original drawings, was assessed using rebar detection, core tests, UPV, and corrosion measurements. Accurate data guided targeted strengthening: micro-concrete jacketing for primary beams and carbon fiber reinforcement for secondary beams. The project highlights that rebar mapping transforms uncertainty into actionable insights, enabling safer, cost-effective, and durable retrofitting of old structures.