The UNIOVI benchmark is a middle-size four-storey, one-bay by two-bay steel frame with bolted connections. It was intended for many purposes but in this paper novelty damage detection is the topic dealt with. A procedure for novelty detection is presented in the paper. It is based on free vibration data corresponding to the first mode of vibration of the structure. The procedure is based on direct time-domain data. The damage is experimentally simulated by adding small masses to the structure. This paper contents a detailed description of the procedure, the experimental set-up and the analysis of results of this new approach.