This research is focused on the experimental characterisation of the compressive behaviour of masonry in existing buildings. The proposed technique is based on in situ core drilling of masonry members. Two walls were built making use of terracotta handmade bricks and lime mortar, without cement, to reproduce a low-strength historical masonry. Core samples were extracted from the walls and then regularized to perform a non-standard compression test in the laboratory. Stack-bonded prisms were also tested under compression. A direct comparison is made between the results from the proposed non-standard tests on core samples and the tests suggested by the available standards on prismatic samples. The proposed minor destructive technique shows to be effective for the mechanical characterisation of existing masonry structures, including historical ones. ; Peer Reviewed ; Postprint (published version)