Water, water everywhere: ingress in underground structures

Many problems encountered with substructures can be attributed to water entering in unintended places, generally in liquid form but sometimes as moisture vapour. Often this will be in the basement of a building, although in some instances the entire structure may be partly or entirely below ground. Water is surprisingly persistent in entering where it is not supposed to. It comes through, up and, although this last is not always considered, down into substructure. Because of this persistence, it is often not straightforward to identify the source of incoming moisture, or to find a remedy. This paper looks at some of the common issues associated with water ingress, the expectations of clients and advisers, and the different methods of specifying performance. It describes some cases encountered over a number of years, where investigations carried out have produced some interesting results and provided new insights into the difficulty of keeping water out of areas where it is not intended to be. The focus is on substructure – basements and buried structures. Leaking roofs or cladding are not considered, other than where the ‘roof’ is the lid of a below-ground structure.