The retrofitting of heritage buildings largely depends on the strength of the mortar between the stones or bricks.  Currently, nano and waste materials represent one of the most efficient and suitable methods for civil and structural applications as reinforcement and repair systems.  Nano Reinforced Mortars (NRMs) have received extensive attention for externally bonded reinforcement of historical and masonry structures.  Historic Cairo is considered one of the most prominent world heritage metropolises and the largest cluster of heritage architecture worldwide.  This work first investigates and elucidates the different properties of the historical lime-gypsum mortars used in monumental buildings. To help identify the characteristics of the historical mortar, different examination methods such as XRD, SEM, EDX and a Compressive Strength Test were used. Next, it investigates the behavior of proposed nanostructured lime-gypsum-based mortars and waste-structured lime-gypsum-based mortars for the restoration and consolidation of traditional mortars used in historical building construction.  Based on the developed knowledge and an extensive literature review, it proposes and validates a methodology for improving the consolidation effectiveness of nano and waste materials, making these suitable products for building heritage conservation. 
The proposed nano and waste lime-gypsum-based mortar specimens is prepared using Natural Hydraulic Lime (NHL), Metakaolin, Sinai Gypsum (SG), Silica fume, Homra (dust of red brick) and sifted siliceous sand.  The previously proposed materials were used in different proposed mix sets in order to make a comparative study of the influence of metakaolin, homra and LBC on the physical and mechanical properties of the mortar mixes.  Next, the study verifies the influence of different lime, gypsum and sand replacement ratios on the properties of the proposed mixes.  Due to the high durability and mechanical properties of category A4 (Lime: Homra: sand: water with ratio of 1: ½ : 3: 2, respectively) and category D1 ( Lime: gypsum: Silica fume: Nano-kaolinite: Homra: sand: water with ratio of  1:½: 1: 1/6: 1/6: 3:2, respectively ) can be considered not only a good durability mortar mixture but also a green restoration process by using waste materials.