Carrageenan, a biodegradable natural polymer, was evaluated as a bioadditive to improve the physical and mechanical properties of adobe constructions. The results show that its incorporation in the mixture during blocks fabrication, or as a coating in existent earth constructions, positively modify their behavior providing water impermeability and resistance to erosion by water drops. Results of mechanical tests also show a considerable enhancement in compressive and tensile strength when the bioadditive is incorporated during the blocks fabrication process. The obtained results show the feasibility of using natural and eco-friendly compounds to modify the behavior of traditional construction materials. © 2017 Elsevier Ltd