In the last three decades, Ethyl silicate is currently the most widely used among stone consolidants; nevertheless, its reduced efficacy on calcitic substrates, where it exhibits some drawbacks that hinder their performance in terms of either mechanical efficacy, compatibility with the substrate and/or durability, make the research for alternative consolidants for carbonate stones necessary. This paper deals with a comparative study between limestone consolidants TEOS-based treatment and phosphate-based treatment severally. The idea of using phosphate-based treatments is forming calcium phosphates (ideally hydroxyapatite) as the reaction product between the substrate and an aqueous solution of a phosphate salt that the stone is treated with. The experimental study was conducted on limestone samples from Saqqara archaeological area, Egypt. Some tests were performed for studying the behavior of the consolidants used. The main aim of these tests is to estimate the consolidants efficiency and investigate the changes of physio-mechanical properties of the studied samples before and after consolidation. The obtained results showed that the hydroxyapatite treatment exhibits a good efficacy in terms of mechanical properties and, compared to treatment based on TEOS, it causes less pronounced alterations in open porosity and water transport properties. This makes the new treatment a potentially valid alternative to treatment based on Ethyl silicate, especially in those situations where the possible presence of water behind the consolidated layer (e.g. in case of rising damp, condensation or infiltration) might threaten the durability of the consolidation intervention.