Nanostructure surfaces are especially promising as highly absorbing targets for high-peak-power sub-picosecond laser–matter interaction. Efficient hot electron, fast ion and thermonuclear neutron production with moderate laser intensity have already been reported. Despite these experimental successes, theoretical investigations on the use of porous targets for the efficient generation of Kα and thermal x-ray emission remain scarce. In this report we use simple physical arguments combined with three-dimensional kinetic simulations to establish the timescales for the destruction of porous targets heated by a PW-class laser pulse.