Thank you, Sandals. Our house is a cavity (hollow) block build. We're about to have it insulated externally so I couldn't help you with your query. However, friends of our had their cavity walls pumped (I think they have a 4 inch cavity) and they haven't had any problems with dampness etc. And it made a huge difference to the house, especially this winter. I would think that if you use high quality exterior paint, you would cut down greatly on the possibility of dampness.