A Guide to Below Grade Evaluation, Investigation and Design

Karim Allana
3 min readMar 5, 2024

Addressing and preempting below grade waterproofing challenges is a critical aspect of project planning and execution. Below grade spaces, those situated below the ground level, are particularly susceptible to water ingress due to their proximity to groundwater and soil moisture.

Let’s explore the sophisticated methodologies and design strategies employed by experts to identify, evaluate, and resolve waterproofing issues in such areas, ensuring the integrity and longevity of the structure.

Initial Evaluation and Investigation

The process of below grade waterproofing begins with a meticulous evaluation and investigation phase. This initial step is crucial for understanding the specific challenges presented by the site. Professionals employ a variety of techniques to gather comprehensive data about the site’s conditions:

  • On-site Visual Observation: The cornerstone of preliminary assessment, visual inspection helps in identifying obvious signs of water ingress and potential vulnerabilities in the structure’s below grade components.
  • Review of Soils and Geotechnical Reports: These documents provide invaluable insights into the soil composition, structure, and water content around the construction site, which are essential for designing effective waterproofing solutions.
  • Analysis of Site Drainage Patterns and Seepage Conditions: Understanding how water moves across and through a site helps in predicting areas at higher risk of water damage.
  • Rainfall Tables and Water Flow Calculations: By analyzing the amount of rainfall specific to the location and calculating potential water flow, engineers can anticipate the volume of water that the waterproofing system might need to handle.
  • Impact of Tides and Water Table Depth: For sites near bodies of water, tidal effects and the depth of the water table play significant roles in below grade waterproofing strategies.

Advanced Techniques for Complex Cases

In scenarios where standard investigation methods are insufficient to fully understand the water-related challenges, more advanced techniques are recommended:

  • Installation of Monitoring Wells: These allow for real-time observation of water table fluctuations and the impact of tidal movements on the site.
  • Water Testing with Soaker Hoses: This method involves artificially introducing water to the site to closely observe how it interacts with the existing drainage and waterproofing systems, identifying weaknesses and areas for improvement.

Design Considerations for Waterproofing Solutions

Once the evaluation and investigation phase is complete, the focus shifts to designing a tailored waterproofing solution. The complexity of below grade waterproofing requires a multifaceted approach, incorporating various components:

  • Single Ply Membranes and Waterproofing Panel Systems: These barriers are designed to prevent water from penetrating the building envelope.
  • Drainage Panels and Drain Pipe Systems: Essential for directing water away from the structure, these components reduce hydrostatic pressure and mitigate the risk of water ingress.
  • Fluid Applied Systems and Epoxy Injection: These treatments offer a seamless waterproof barrier and are particularly useful for remedying existing water damage or reinforcing areas of high vulnerability.

It is imperative that these solutions are designed by professionals who are well-versed in below grade waterproofing. The unique conditions of each site demand a custom approach, combining different materials and techniques to address the specific challenges at hand.

The intricacies of below grade evaluation, investigation, and design underscore the importance of a meticulous and informed approach to waterproofing. By employing a comprehensive suite of investigation techniques and leveraging advanced design principles, construction engineers can develop effective strategies to protect structures from the detrimental effects of water ingress. This not only ensures the structural integrity and longevity of the building but also safeguards the investment made by stakeholders. Engaging with experienced professionals who can navigate the complexities of below grade waterproofing is essential for any construction project aiming for success.

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Karim Allana

Karim Allana is founder and CEO of Allana Buick & Bers. He is an industry leader in building envelope architectural engineering and construction management.