This paper presents the results of analytical work which aimed to explore potential sources for the lime mortar used in the Hadrianic fort baths and a third-century repair to Hadrian’s Wall at Wallsend, UK. It is generally assumed that quick lime for mortar is produced close to the source, however, as yet, no archaeological evidence of kilns has been found in the Wallsend area. After extensive analysis the mortars were found to be very different in characteristics and suggest variable sources for the quarried limestone and for the aggregates used to manufacture the mortar. Precedence exists in other locations for quicklime to be sourced from kilns set at some considerable distance from Roman construction sites. It is only at Housesteads and Vindolanda, sited close to Carboniferous Limestone outcrops, that Roman lime kilns have been discovered to date. Therefore the investigation included a number of potential sources in the vicinity of Housesteads as well as Permian limestones at Trow Point which is geographically the closest source of limestone. Results suggest that Carboniferous limestone was the most likely source for some of the mortars analysed which may suggest that areas for lime production are less numerous than previously thought and may even have been concentrated around one area.