This paper presents an experimental study aimed to investigate the mechanical and thermal properties of a traditional rubble stone construction, namely Bungaroosh. Bungaroosh was often used in the South-East coast of England during the early 19th century; it can be found prevalently in the city of Brighton and Hove, nestled in the center of this geographic setting, in the walls of many traditional (pre-1919) dwellings and the rear elevations and party walls of grand Regency buildings. This research project aimed to investigate the material characteristics, compressive strength, and thermal conductivity of Bungaroosh constructions to provide useful data for the structural and/or energy modelling of buildings made with Bungaroosh. For this purpose, 18 replica Bungaroosh samples were made and tested in the laboratory to assess their compressive strength and thermal conductivity, after exposing them to three sets of environmental conditions characterized by progressively increasing relative humidity (RH) values. The results were triangulated with secondary data from the literature. The tests produced an average compressive strength of 1.47 MPa which decreases with exposure to higher RH values; the average thermal conductivity of the samples investigated is 0.26W/(m·K) and it increases with exposure to higher RH values. These data, although specific to the samples investigated, can constitute useful reference values for structural and thermal analysis of traditional buildings in the South-East of England when in-situ testing methods might not be applicable.