Mastering blindside waterproofing: A proactive, integrated approach

Conclusion

The process of designing and installing a blindside waterproofing system requires a coordinated, multi-disciplinary approach to achieve the greatest likelihood of reliable performance. It is possible to avoid many of the common blindside waterproofing surprises by taking a proactive and integrated approach early in the waterproofing design process to anticipate and address the variables discussed above. Consider these takeaways:

• Coordinate SOE design and foundation structural design with waterproofing design. Encourage a meeting as early in the project as feasible between the SOE designer and architect, structural engineer, general contractor, waterproofing installer and manufacturer, and waterproofing consultant and/or commissioning provider. Collectively examine project-specific SOE details and configurations and work with the project team to avoid or limit penetrations and precarious SOE conditions, such as those described above. As construction commences, the project team should confirm the blindside waterproofing shop drawings are coordinated with the finalized SOE shop drawings. Unique or challenging waterproofing details should be examined during waterproofing preinstallation meetings.
• Scrutinize site-specific geotechnical/environmental conditions and subgrade drainage design. Prior to specifying and detailing the waterproofing system, review the geotechnical and environmental report to understand (and communicate to the waterproofing manufacturer) site-specific groundwater conditions and soil/groundwater contaminants. Coordinate the blindside waterproofing design with the project-specific subgrade drainage design, if applicable.
• Coordinate waterproofing design with concrete placement method and formwork/reinforcement materials. Substituting shotcrete (on a project where the blindside waterproofing was designed for cast-in-place concrete) can result in incompatibilities that are detrimental to waterproofing performance. Project teams can accommodate the use of shotcrete if declared early enough (e.g. during design), and if the blindside waterproofing design is coordinated accordingly, including with input from the manufacturer. Project teams should place particular emphasis on using properly trained and qualified shotcrete nozzle operators. In addition, for any concrete placement method, specify permissible concrete placement/reinforcement materials (e.g. formwork, rebar chairs), which are suitable for pairing with the basis-of-design waterproofing.
• Ascertain duct bank configuration and installation sequence. Engage the general contractor as a liaison to ascertain information about the duct bank, so that applicable, sound, and constructible details can be developed in advance of the construction process.