Moisture-induced deterioration is a major concern in historical buildings due to the high porosity of traditional construction materials. Restoration plasters must be breathable and compatible to regulate moisture transport, prevent salt crystallization, and enhance durability. Sustainable materials like clay-based binders and lightweight aggregates improve moisture control while reducing environmental impact. Expanded perlite (EP) and crushed expanded clay (CEC) modify pore structure and capillary absorption, but their interaction with curing conditions remains insufficiently studied. Existing studies explore curing conditions and aggregate effects separately, yet their combined influence on moisture transport and durability under real conditions is unclear. This study investigates the impact of curing conditions and aggregate type on porosity, capillary absorption, and bulk density in cement-clay composites. Results show EP and CEC increases porosity by 40–70%, leading to 150–270% higher capillary moisture content under real-world curing conditions compared to standard curing. However, CEC facilitates faster drying. These findings highlight the need to control the interaction between the curing conditions and the type of aggregate in order to achieve a balance of porosity, bulk density and moisture transport properties to improve the durability of the material. Future studies should apply advanced microstructural analysis (MIP, X-ray CT, NMR) to further explore pore connectivity and long-term performance.