Constrained volumetric shrinkage of the solidifying material layers during additive manufacturing (AM) causes warpage of 3D-printed parts. The geometry of the part affects the magnitude and profile of the warp deformation. This paper aims to characterize warpage as a function of part height in the fused deposition modeling (FDM) process. A thin vertical wall geometry is modeled for this study with part height as the geometric variable. Optimal process conditions are maintained on an open 3D printer to prevent detachment of the parts from the build plate during fabrication. Temperature distribution across all layers is recorded throughout the fabrication of each sample. The measured warpage profiles of the samples indicate that warpage occurs even in the case of strong build plate adhesion. A previously unreported downward curling is observed in parts of lesser height. The warpage magnitude in upward curled samples increases with increasing part height partially following earlier reported trends. An optimum build plate temperature ensures part-build plate adhesion throughout the fabrication. Yet, shrinkage in the material is still constrained resulting in a stress distribution that causes downward warping. The temperature distribution across the part layers w.r.t the glass transition temperature affects the warp deformation profile. The present work attempts to provide a unified explanation for upward and downward warpage in 3D-printed parts. These findings necessitate an improvement in the numerical models to predict downward warping.