In the present work we report on the development of a low cost interrogation system of fiber Bragg grating sensors for structural health monitoring. The developed scheme uses two gratings and a directional coupler as sensing point, and it includes self-compensation of temperature effects. The reading equipment consists of a standard photodiode for telecom applications with custom signal-conditioning electronics. The characterization of multiplexed sensors, carried out in real framework conditions, shows that the system can work in a temperature range of -20÷+40°C, making strain measurements up to at least 320με with an accuracy of ~3% and an acquisition rate of 12 samples/min. Further, a budget evaluation is drawn to asses the feasibility of our interrogation system as a low cost solution to increase the extent of structural health monitoring in funds-limited applications.