The need for the formulation of mortars for repair of ancient Roman renders in the archaeological site of Conímbriga brought about the need for a study of the rendering solutions existent therein. Various samples were extracted and analysed by means of acid attack followed by determination of particle size distribution, execution and visualization of thin sections, thermal analysis and mineralogical and chemical analysis using XRD and XRF. This paper presents the results of four of the Conímbriga mortars; the results show similarities in terms of the raw materials that were used and crushed ceramic particle size.