Below-grade waterproofing systems can be critical features of building enclosure design, particularly when the structure has a deep foundation. As the foundation goes deeper, there is a greater likelihood that it will encounter the groundwater table and hydrostatic conditions, which makes choosing the right below-grade waterproofing system even more important. When selecting and designing a below-grade waterproofing system, the primary factors to consider include the type of foundation system, the project’s site conditions, product performance properties, and construction sequencing. The design specifications for a building’s foundation are influenced by the building size and structural system, as well as the site’s soil and geological composition. Foundation systems are typically either categorized as shallow foundations or deep foundations. Shallow foundations are used when the structural loads can be adequately distributed to a relatively shallow level of soil. Examples include structural slab-on-grade foundations, footings, and grade beams. Deep foundations are used when there are more significant loads that need to be transferred to deeper soil or bedrock. These types include piles, caissons, and drilled shafts, among others.

LEARNING OBJECTIVES 

After reading this article, you should be able to: 

• Identify key principles used in determining below-grade waterproofing selections
• Understand project decisions critical to the development of below-grade waterproofing systems for deep foundations
• Describe appropriate below-grade waterproofing systems based on site conditions and foundation types
• Explain construction challenges that may occur during installation of below-grade waterproofing for deep foundations