<p>Many of our cities are running out of usable construction space for large buildings. New buildings are reaching new heights and new depths, often extending several stories below-grade. This presents challenges for waterproofing, particularly when building foundations extend below the groundwater table. With climate change and sea-level rise, many geographic areas will increasingly need to consider groundwater.</p><p>Building code requirements, especially in seismic regions, often require engineers to design movement joints or separation joints in below-grade structures. But foundation waterproofing materials are designed to seal around a building, not a void or an excavation. Structural joints are more susceptible to leakage, and higher volumes of leakage, than areas with solid backup.</p><p>We review design considerations for movement joints and present two case studies: a parking structure with structural separation joints between exterior shotcrete shear walls; and a hospital campus relying on below- grade expansion joints between buildings with differing foundation systems. In both, the presence of below- grade joints necessitates more complicated detailing and installation.</p><p>Experience shows us the best practice is to waterproof the building, not the void. Performance is best when the below-grade structural walls provide a solid, continuous substrate. Where movement joints cannot be avoided, we recommend designing structural elements to also meet the needs of the waterproofing system.</p>