Structures are expected to be designed with the lowest cost and a longer lifetime, without catastrophic service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber exhibits these characteristics and is a more appropriate candidate than most other structural materials, particularly in terms of fire protection, lightness, and seismic resistance. In recent years, timber has been used to design of low-rise commercial and taller residential buildings due to these significant advantages. However, timber degradation can occur as a result of biological decay of the elements and overloading that results in structural damage. Therefore, the load carrying capacity of older timber buildings can be questionable, particularly against lateral boards. This paper investigates damage detection and performance evaluation of older multi-storey timber buildings. In this process a method was implemented in order to provide real-time performance and damage information of a case study building before and after retrofitted improvements. For this purpose, damaged members are identified and then are retrofitted with engineered timber sandwich beams or Sprayed Fibre Reinforced Plastic (SFRP) to extend the life of the structure. Non-linear finite element analysis was carried out to study the behaviour of the structure subject to simulated gravity and lateral loads and to validate the effectiveness of the method of damage detection. This study show that the proposed method is suitable for structural damage detection of aged timber buildings and also the retrofitting methods cited can potentially improve the performance and load carrying capacity of the structure.