The impact of boundaries on electrical conductivity and chemical diffusion is discussed. The equilibrium point defect chemistry of boundaries is described by the core-space charge model. Conductivity effects are briefly touched upon. The chemical transport is discussed in more detail using a linearised Nernst-Planck-Poisson set of equations. In the steady state the model is applied to three simple situations: (i) enhanced diffusion along, (ii) hindered diffusion across laterally homogeneous boundaries and (iii) diffusion through poorly connected grains. In the transient regime the impact of blocking grain boundaries is considered.