<p>Masonry walls are vulnerable but are the principal load-bearing members in many residential and heritage buildings worldwide. These walls required practical and affordable solutions to improve their longevity and safety. This work uses numerical simulation to explores the application of the Ultra High-Performance Concrete layer to improve the in-plane loading performance of existing masonry walls. The numerical simulation uses the finite element modelling technique, incorporating the Concrete Damage Plasticity constitutive model within a detailed micro-modelling approach enhanced by a surface-based cohesive approach to simulate a comprehensive 3D representation of the masonry wall. Different parameters, including the thickness of the ultra-high performance concrete layer and the aspect ratio of the wall, have been investigated. The study revealed a significant improvement in in-plane shear strength, stiffness, and dissipated energy of the wall. Additionally, the results indicated that increasing the thickness of the ultra-high performance concrete layer improves the overall wall performance, with diminishing returns observed beyond 40&#xa0;mm. Furthermore, optimal structural integrity was noticed within a particular range of aspect ratios, highlighting the effectiveness of the strengthening approach. The results highlight important parameters that contribute to improving structural integrity and efficiency, enabling valuable insights for future design and engineering applications.</p>