In this article an overview is given of the equations describing the coupled heat, moisture and salt transport including phase transitions in porous building materials which have been implemented in the simulation program Delphin 5. Based on a convection-diffusion model for transport of binary salt solutions the simulation code was extended by a transport model for salt mixtures. The model allows description of transport and phase transition processes of Na-K-Cl-NO(3)-SO(4)-H(2)O systems. A kinetic model for the phase transitions crystallization and dissolution is presented that can also be used for hydration and dehydration reactions. Particular focus also lies on the description of models for the calculation of thermodynamic properties of salt mixtures and their impact on material functions and on heat and moisture transport processes.