A measuring system adapted to the needs of civil engineering structural monitoring is presented. It is based on low coherence interferometry in standard singlemode fibers and has a resolution of 5 micrometers , an operational range of 7 cm, stability over long periods (at least 1 year) and insensitivity to variations of the fiber losses. The portable reading unit doesn't need to be connected to the sensing fibers permanently and can thus be used to monitor multiple structures reducing the costs of the instrumentation. This paper presents the operating principle of this system and different techniques used to install the sensing fibers in large concrete structures, timber and mixed timber-concrete structures as well as on metals.