At low frequency, modal synthesis is usually used to solve the vibrational fluid-structure interaction problem. The modal technique application for elasto-poro-acoustic complex structures requires a modal description of the poroelastic vibroacoustic behaviour. Some recent works concerning the application of modal techniques for the displacement pressure equation of the generalized Biot’s model were published. Dazel proposes a modal decomposition based on the use of complex modes. This work consists in projecting the poroelastic system on a truncated basis of damped and coupled modes. In the mode calculation, the author takes into account fluid-structure interaction, viscous and thermal dissipations but structural damping is neglected. This paper presents a modal approach allowing to reduce the size of the poroelastic matrix system and to predict more effectively the porous material vibroacoustic behaviour. Starting from Dazel’s works, this modal approach is based on complex modes, modal synthesis, modal projection and modal superposition techniques. The originality of this paper is to take into account the porous material structural damping in the poroelastic mode calculation.