Many existing reinforced concrete (RC) buildings in developing countries were built using inadequate construction practices and have insufficient lateral load resistance, which increase their seismic vulnerability. As demolishing these buildings may not be not cost-effective, their vulnerability can be mitigated by strengthening the concrete elements. Recent research has developed an economical, fast and non-intrusive retrofitting technique using Post-Tensioned Metal Straps (PTMS). The PTMS technique involves the post-tensioning of high-strength high-ductility steel straps around concrete members using tensioning tools as those used in the packaging industry. This presentation will show recent research that demonstrated experimentally the effectiveness of the PTMS technique at enhancing the behaviour of concrete elements, including a real full-scale two-storey RC building tested on a shake table.