Maintenance and repairing or ancient buildings requires efforts and a wide knowledge of the structures. However, in many cases, the constructive methods, the distribution of supporting elements and the materials are unknown. There are two main causes of this uncertainty: the lack of information and drawings due to the age of the buildings, and the misinformation about past restorations, damages and alterations of use and structures. This paper presents a GPR assessment of two terraces of ancient buildings, placed in the Eixample neighbourhood of Barcelona city (Spain). Common offset radar data was used to acquire data on the terraces of the buildings, with an 800 MHz centre frequency antenna. In one case, GPR images show structural changes as consequence of rehabilitation. The other case study is characterized by significant variations in the built structural supporting structures, including orientation and material types. In both cases, GPR images allowed to determine the structural supporting structures. The results highlight the capability of the method to determine the position, orientation and shape of structural elements and, also, to differentiate between wooden and metallic members. © 2019 24th European Meeting of Environmental and Engineering Geophysics. All rights reserved.