Fault tolerance in wireless sensor networks (WSNs) has been studied extensively by computer science researchers and they proposed many fault-tolerant schemes for various applications including target and event detection. However, these schemes would fail in a particular application of WSNs: structural health monitoring (SHM). Different from other applications of WSNs, detecting structural damage requires significant amount of civil domain knowledge and utilizes different detection model. Meanwhile, researchers in civil engineering also proposed some fault-tolerant SHM algorithms. However, these algorithms are all centralized and not applicable to resource-limited wireless sensor networks. To our best knowledge, we are the first to address fault tolerance problem in WSN-based SHM. We target faulty sensor reading, one of the most difficult types of sensor fault to be detected, and propose a fault-tolerant SHM approach. The proposed approach is lightweight and it is able to disambiguate structural damage from sensor faults. The effectiveness of the proposed approach is demonstrated through both simulation and real implementation.