The transition towards next generation communications has increased the need for fast and accurate propagation models that can predict all aspects of the wireless channel. This paper develops a very accurate approach for indoor propagation modelling based on the volume electric field integral equation (VEFIE). The three-dimensional form of the VEFIE is used to predict frequency domain characteristics. Whilst, a 2D to 3D model is developed based on the 2D VEFIE to perform accurate and efficient time domain predictions. The 2D to 3D model applies correction terms to the solution of the 2D VEFIE to account for three-dimensional propagation. Both models are compared against frequency and time domain measurements as well as popular empirical models for both scenarios.