The objective of the paper is to present the effect of moisture in concrete on the fire resistance of side-plated reinforced concrete (RC)beams. For this purpose an adequate newfinite-element (FE) procedure is presented. The paper concludes with a parametric study, examining the impacts of the vapor-tight side plates, high initial moisture content and low initial permeability of concrete of the selected RC beam on the rate of the risk of concrete spalling. Plating techniques present a popular modern engineering solution of structural retrofitting. Until this time a broad range of different plating solutions has appeared in the market (i.e. the tension-face plating technique, the side-plating technique, the U wraps, etc.), nevertheless, in the engineering practice, the tension face plating solutions have been mostly implemented. A similar trend is detected in the published reports of the scientific investigations. So far, a vast amount of research has been executed on the tension face plated beams, but almost none has been dedicated to investigating structural behavior (especially such as in fire) of the alternatively plated (e.g. side-plated) beams. Another problem which applies to any kind of concrete or composite concrete structure in fire is its thermal and mechanical damage, the former caused by the physical and chemical decomposition of the material at elevated temperatures, and the latter induced by the stresses due to restrained thermal dilatation or applied external mechanical loads. The higher the rate of concrete damage, the more deteriorated are the mechanical characteristics of the concrete (such as compressive strength and elastic modulus) and the more increased is the material permeability. In addition, the heterogeneity of concrete should be explicitly considered. Concrete consists of the solid matrix representing the hardened cement paste and aggregates as well as of pores. These are filled with water (liquid, adsorbed or chemically bound) and with the gaseous mixture of dry air and water vapor. Due to the presence of fluids inside the concrete pores and its pressure and concentration gradients, generated on account of phase transitions (water evaporation and vapor condensation) and concrete permeability gradients, mass fluxes of water and air inside the pores emerge and, consequently, the heat is not only conducted but also convected through the material. A part of the evoked mass fluxes shifts towards the heated surface of the body, while the rest moves inwards - towards the cooler layers, where vapor condenses and increases the level of pore saturation. As a consequence, the permeability of the material is substantially diminished in this region and speed of passing water and gas flows is reduced. The emerged clogged zone finally causes a rapid rise of pore pressures in front of the zone, accelerated crack propagation in this area and, in most severe cases, explosive spalling of the damaged material. In scientific literature of the last decade, several mathematical models have been proposed for fire analyses of heterogeneous concrete structures. In general, two fundamental groups of such models can This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.