With space at a premium in many urban areas, developers are digging deeper foundations to increase the square footage of high end residential, commercial and mixed-use building projects. The lack of above grade space is leading to increased use of basements for storage, archives, retail space and parking space. In other cases, a deep foundation may be needed due to large design loads or poor soil at shallow depths. In San Francisco for example, the Salesforce Tower is built on rock by way of cast-in-place foundations extending down approximately 265 feet.
Digging deeper foundations has many advantages, but also introduces many challenges that need to be addressed at the design phase, particularly for waterproofing. These challenges include: