Historical buildings are the cultural heritage of the world. Preservation of historical buildings is important in the past and today. In particular, material fatigue, environmental vibration effects and natural disasters that occur over time cause great damage to historical structures. It is thought that many historical buildings will not reach the next years due to neglect. In order to prevent this situation, historical buildings should be maintained and strengthened if necessary. In addition, historical buildings should have sufficient stiffness to prevent collapse against pre-disaster situations. Stone barrel vaults are one of these historical cultural heritages. Many stone barrel vault type historical structures are frequently encountered today. In order for stone barrel vaults to be transferred to the future, care should be taken and they may need to be strengthened periodically, especially after disasters. For all these reasons, in this study, the foam concrete method, which is one of the retrofitting methods of buildings, is mentioned. Thus, the effect of the foam concrete method applied on an exemplary stone barrel vault on modal parameters has been demonstrated. In this comparative study, it was observed that the stiffness of the stone barrel vault increased with the foam concrete method. As a result of this study, it is suggested to retrofitting the stone barrel vault with the foam concrete method, taking into account the state of the stone barrel vault and environmental factors.