With the constant increase of the population, especially in urban areas, new living space is needed. Additionally, the housing requirements from the residents have changed significantly in comparison to the requirements from the 19th and beginning of the 20th century. For this reason, many existing buildings are being extended and/or adapted to meet new housing requirements. In case of such interventions, the structural engineers are obliged in some cases to provide and prove the earthquake resistance of the existing building. However, in many cases this can lead to difficulties, as many existing buildings are built according to traditional rules without taking earthquake loads into account. The present work deals with the buildings from the period between 1840-1920 and the possibilities of their earthquake strengthening. Firstly, the normative basis for treatment of existing buildings is presented. Secondly, answers will be given to the questions, when and to what extent one existing structure should be strengthened and which regulations should be applied. In addition, the calculation methods for earthquake analysis according to EN 1998 are presented, whereby the push over analysis, being the most suitable method for determining the load-bearing capacity of existing structures, is presented in detail. Finally, the most frequently used earthquake strengthening techniques for masonry buildings in practice are going to be presented and analysed. Depending on the goal to be reached, the strengthening techniques are going to be divided into two groups, namely, techniques for wall strengthening or wall replacement and techniques for achieving the load distribution effect on the slab level.