Fire design procedures for RC columns and shear walls assume that structures are designed according to ambient-temperature (AT) standards, whose partial safety factors can provide an intrinsic fire safety margin. However, the magnitude of this margin in fire behavior has not yet been quantified. This study quantifies the intrinsic fire safety margin by comparing the fire performance of RC columns and shear walls subjected to two load levels derived from AT: (i) the ultimate load obtained from nonlinear FEA model, representing the "real" structural capacity, and (ii) the “design load” obtained by standardized AT design criteria. Seven rectangular cross-sections with identical reinforcement ratios (∼3%), Ø20 mm longitudinal rebars, and 40 mm concrete cover were analysed under the ISO 834 fire considering three exposure cases: single-face heating adjacent (FC-I) and opposite (FC-II) to the load eccentricity, and four-face heating (FC-III). The “design load” increased the FRR by up to 180% than prescribed by the fire standards, corresponding to an intrinsic fire safety factor of 1.8–2.8. The heated-face orientation modified the FRR by up to 250%, whereas four-face heating reduced the FRR by 55–80%. Increasing the cross-sectional depth from 300 to 1200 mm increased the FRR by up to 470%. The results demonstrate that AT design provides an intrinsic fire safety margin that is not explicitly considered in current structural fire design standards.