This paper deals with the potentialities and technical and methodological issues associated with the use of lumps of not completely melted lime as material suitable for the radiocarbon dating of aerial lime mortars and plasters. In fact, the identification and selection of single aggregates of unmelted lumps allows one to reduce the possible contamination resulting from external sources of carbon such as “14C-dead” limestone in sand added to the mixture during preparation. This procedure results in the possibility for accurate 14C determinations from single pieces of masonry, supplying important information about the construction phases of historical buildings. The potential of this approach is shown by presenting the results of the archaeological study on the walls of San Nicolò of Capodimonte church (Camogli, Genoa, Italy), where this technique has been successfully applied to obtain absolute ages of different parts of the building. The obtained results were then compared with the information gathered from historical sources and with stratigraphic and other archaeological studies.