A mechanical based method for the evaluation of the seismic capacity of masonry buildings’ classes in terms of damage limit states is presented: the purpose of the study is to achieve, in the framework of vulnerability analyses at territorial scale, reliable values for the damage level of vulnerability classes of masonry buildings, depending on the seismic input level. This approach is, in fact, designed as a “1st level” tool based on easily traceable information provided by expeditious surveys. Once identified a limited number of typological, physical and mechanical parameters that are necessary to define each vulnerability class, a significant number of simplified models of masonry buildings belonging to each class has been created. Non-linear static analysis of these models allowed the creation of bilinear elastic perfectly plastic capacity curves: the displacement capacity described by these curves is related with the actual displacement values required by seismic intensities associated to different return periods. It is so possible to identify, for different vulnerability classes and different seismic inputs, the loss of capacity in terms of damage level of each building. An application of the method to models representative of masonry buildings in the historical centre of Sulmona, in L’Aquila province, and a comparison of the results with others obtained with other methodologies of assessment are presented.