In present paper, a linear thermoelastic theory for porous materials is established by extending the existing theory, in which the strain relaxation and the thermal relaxation are included. Based on the thermodynamic laws, the constitutive relations are derived, and then the corresponding constitutive equations are obtained by specifying the generalized free energy. Further, by combining the existing theory, the non-Fourier's heat conduction law and the obtained constitutive equations, the linear thermoelastic theory for porous materials is formulated. To apply the established theory, the transient response of a half-space with voids is considered. The half-space with voids is subjected to a thermal shock and a mechanical shock simultaneously on its bounding surface. The problem is solved by means of Laplace transform and its numerical inversion. The distributions of the non-dimensional temperature, displacement, stress as well as the volume fraction field are obtained and illustrated graphically. In calculation, the effects of the thermal relaxation factor, the strain relaxation factor and the magnitude of the mechanical shock on the considered variables are examined and discussed in detail. © 2020 Elsevier Masson SAS