Below-grade waterproofing provides challenges which are quite different from, and often more demanding than, super-structure works. Site conditions are typically less than ideal, accessibility may be limited, the stresses on the waterproofing system are more varied, and repairs – if necessary – can be more disruptive and costly. This presentation looks at common defects and problems, the different levels of dryness required for basement structures according to their functions, and selection criteria for waterproofing systems. It aims to help Designers understand the considerations which go into selection of best-fit solutions.