The Historic Jeddah city is the forefront of the Saudi Arabia heritage sites that UNESCO recently registered in the World Heritage List. Most of its buildings were constructed with multiple-leaf masonry walls using marine-origin of fossiliferous limestone that vernacular name is "Mangabi". These stones are characterized by high porosity, low density and weak mechanical strength. Unfortunately, most of previous studies merely concerned architectural aspects of these buildings and their urban. This paper presented some parts of the intensive experimental campaign by the authors that focused on various structural aspects and strengthening techniques of these buildings. It aimed to evaluate the enhancement of physical and mechanical properties of their stones by injection with either nano-lime or Wacker OH-100. Different parameters were taken into consideration to evaluate the short-term efficacy of the consolidating materials after both treatments. Thirty-six cubic stone specimens of 50 mm side-length were prepared from ruins of unregistered heritage buildings. Twelve specimens were treated with the nano-lime 'CaLoSiL^®' of IP5, E25 and E50 ready concentrations, using brushing and injection, while another twelve were treated with Wacker OH-100. Both types were left thirty days for polymerization and carbonation processes of the consolidants to complete in standard conditions. Then, standard physical (i.e. bulk density, apparent porosity and water absorption) and uniaxial compression tests were conducted for both untreated and treated specimens (three specimens per each test). Besides, X-Ray diffraction and digital, polarizing and scanning electron microscopes were utilized for microstructure examinations of the specimens. Results and recommendations were derived.