Earthquake loads can induce out-of-plane deformations in thin reinforced concrete (RC) walls that may lead to member out-of-plane failure or cause a premature in-plane collapse. Such instability phenomena have been observed after the recent earthquakes in Chile (2010) and New Zealand (2011). Walls with single layer of vertical reinforcement are more vulnerable to instability issues than the typical two-layer design. However, high material costs and the increasing demand of housing for low income population in Latin America (namely Colombia) over the last few years has prompted city administrations to build medium to high rise RC buildings using walls with single layers of vertical reinforcement. The results of a recent experimental campaign on thin RC walls performed by the authors confirmed the relevance of this topic, underlining the need for further investigations to study the effect of different parameters on the out-of-plane response, such as loading history, wall thickness, and longitudinal reinforcement ratio. This effort is currently being carried out by idealizing the wall boundary region—which primarily triggers the instability mechanism—as an equivalent column axially loaded in cyclic tension and compression, as commonly hypothesized by the existing phenomenological models. This paper presents the first results of a numerical study consisting of the application of a beam-column model.