Water interacts with buildings at a range of overlapping scales, from envelope to pore. For 30 years building conservators have made practical field and laboratory investigations at the scale of elements such as walls. These have increased both our practical understanding, and our ability to deal with failure. This paper presents the argument that they also fundamentally outline a far more complete picture of the way that moisture travels into and through building systems under normal conditions. This paper draws widely on research by the authors and others, to propose a consistent and simple picture of the interaction of water with ‘traditional’ buildings based on permeable materials. While some of the accepted wisdom is confirmed, other theories are challenged; particularly those around the nature of water transfer.