This work highlights the importance of applying suitable methods for the design of air-hardening lime mortars with the correct water dosage and binder-to-aggregate ratios. To this end, the recently developed ‘wet packing method’ has been used to assess the optimum water-to-binder ratio at which the packing density is achieved in lime mortars with different binder-to-aggregate proportions. To support the validity of this method, it has been compared with other standardized methods of determining the bulk density of the dry granular components and the consistency of the mortar pastes. The reliability of the wet packing method has then been verified by studying the mineralogical, textural and mechanical properties of mortars after 2 and 6 months of carbonation. Results showed that although the wet packing method seems to be more realistic than the majority of standards used for the determination of the packing density and workability in granular mixtures, it is not totally suitable for the preparation of air-hardening lime mortars with good performances in the fresh and hardened state.