This chapter uses a mechanical method that involves non-linear analysis with deterministic and probabilistic approaches, as well as procedures of analysis based on limits states defined by displacements, in order to evaluate the behavior of a low rise RC building with plan irregularity designed according to Venezuelan codes and subjected to seismic actions. By using adequate structural models and computational tools, the seismic behavior of the building is obtained in a suitable way. Among these tools, the quadrants method was chosen, which provides the rapid assessment of the seismic capacity of a structure through its non-linear response. The results of the research show that the current design of this kind of structures is not safe when they are designed for the maximum seismic actions prescribed by codes. Therefore, it is necessary to review the design procedures in order to fulfill the goals of the performance-based design.