Blindside waterproofing
Blindside waterproofing involves installing the drainage course and waterproofing membrane prior to placing the concrete vertical walls. In this process, the excavation is typically supported by soldier piles and lagging, soil nailing, shotcrete, or caisson walls. In addition, a drainage mat is applied overtop of the shoring wall, with the fleece side directly facing the wall. This configuration facilitates proper drainage and a reduced hydrostatic pressure.
When using a polyurea membrane, a fleece carrier sheet on the reverse side is typically used to receive the spray-applied waterproofing membrane (Figure 3). The spray-applied membrane is installed over the interior fleece, at a thickness specified by the manufacturer (typically 80 mils), although deeper foundations will require a thicker application. The added thickness of the polyurea waterproofing helps resist the higher water pressures at greater depths.
After detailing is complete and the monolithic waterproofing layer is applied, the concrete foundation wall is poured into place. Polyurea serves as an efficient solution to blindside waterproofing, expediting the installation process while delivering a seamless, resilient, and durable waterproofing layer.
Positive side waterproofing
Positive side waterproofing is an external system of waterproofing applied directly to the exterior surface of the structure being waterproofed (i.e. foundation wall). An effective positive side waterproofing system will protect the structure and its components from moisture ingress. Prior to the application of the polyurea waterproofing membrane, it is good practice to ensure the CSP aligns with the manufacturer’s written instructions.
After the primer is installed and cured as recommended, the polyurea waterproofing system can be sprayed directly to the exterior concrete face, creating a damage-resistant monolithic waterproof barrier around the structure. Typically, the use of drainage and protection boards placed over the top of the membrane have been used to protect the integrity of the membrane, and to relieve the hydrostatic pressure from the surrounding area. Recent testing has shown these drainage and protection boards can be eliminated due to the waterproofing’s structural characteristics.
Canada experiences numerous cold months, however, construction does not stop. Even in such conditions, polyurea membranes can be applied to substrate temperatures as low as -10 C (14 F). To meet energy requirements, insulation can be installed over the waterproofing membranes. Traditional exterior below-grade options could include closed-cell sprayed polyurethane foam (ccSPF), extruded polystyrene (XPS), expanded polystyrene (EPS), and mineral wool.
Conclusion
Whether it is historical structures such as the Great Pyramids of Giza, or addressing the Sunken Foundations of Gatineau, waterproofing materials and techniques play a vital role in preventing water infiltration into structures.
Water stands as the primary cause of building component degradation, making it crucial to prevent its entry into the assemblies, particularly below-grade ones. While adequate design and construction practices must be at the forefront, incorporating advanced materials such as polyurea can significantly enhance performance.
A high-performing waterproofing membrane should be easy to install, monolithic, damage-resistant, chemical-resistant, and capable of withstanding high levels of pressure—these are all attributes of polyurea.
Polyurea is a reliable and durable material suitable for various applications beyond blindside and positive side waterproofing, and adhering to manufacturer’s written instructions and following the guidance of the contractor can help ensure a long-lasting waterproofing system. Lastly, trained third-party installers equipped with state-of-the-art computerized application reactors can help minimize the risks associated with poor and inconsistent application.
Notes
1 Learn more about water intrusion,
www.architectmagazine.com/technology/when-it-leaks-it-pours
Author
Rockford Boyer is an experienced building science leader at Elastochem, with more than 20 years of expertise in sustainable building design. He holds an undergraduate degree in civil engineering and architecture, as well as a masters in building science, and is a member of Passive House Canada and the Ontario Building Envelope Council (OBEC). He is also a part-time professor at Sheridan College, where he teaches in the architectural technology program, sharing his knowledge and expertise with future generations of architects and designers
