The internal forces in stiffeningwalls are usually determining by numerical methods. Extreme values of forces and displacements can be achieved without significant problems. The numerical model is always labour-intensive; therefore, it is not used for single-family or multi-family buildings with a simple wall layout. To calculate efficiently internal forces in such walls uses an analytical model. Eurocode 6 (prEN 1996-1-1: 2019) does not provide specific guidelines for determining geometrical characteristics and procedures for calculating the values of internal forces in the stiffening walls. The use of numerical methods and other reliable methods was allowed. The paper presents the adaptation of the total stiffness method to determine internal forces in a building with a simple wall system. The method was based on dividing the masonry wall with openings into pillars, lintels, bottom sprandels and flanged walls. The analytical results were compared with linear-elastic FEM calculations. It has been demonstrated that flexural stiffness, shear stiffness and localization of rotation centre (RC) had a crucial impact on masonry structure.