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Blindside waterproofing can prevent water penetrating a building’s foundation

Peter Caulfield
Blindside waterproofing can prevent water penetrating a building’s foundation

Because of the continuing COVID-19 pandemic, BUILDEX Vancouver and Alberta combined to hold the recent BUILDEX Amplified 2021.

The new format featured small in-person events and online educational programs.

The subject of one of those educational programs, Overcoming the Challenges of Blindside Waterproofing, was how the sources of water penetrating a building’s foundation are often the result of design or installation oversights.

The presenter was Ashley Foster, a technical representative at ESP Engineered Site Products (2019) Ltd. in West Kelowna, B.C.

Foster’s presentation reviewed waterproofing system selection and the main elements of substrate specification and quality control. 

Related topics that were covered in the talk were the challenges of blindside waterproofing, the importance of shoring systems to waterproofing performance and detailing and design.

Foster said blindside waterproofing is a type of property line construction that is a newer method of waterproofing compared to traditional back-filled methods.

“Blindside waterproofing is used when there isn’t access to the outside outer wall,” she said. “Waterproofing is applied to a substrate, such as shotcrete shoring, wood lagging or metal sheet piles, and then concrete is poured against it.

“We often see blindside waterproofing used in cities where there are tight worksites when an entire footprint of land is being developed.”

Foster said the biggest advantage of blindside waterproofing is that it uses shotcrete, which many people believe to be stronger than cast-in-place concrete.

“Blindside waterproofing applications and system installation can be challenging,” said Foster. “There are different types of form-type systems the concrete trades use, and different types of rebar anchoring systems the steel trades use. This is important because both systems interface with the waterproofing system, and with high traffic on the work site the waterproofing could get damaged.”

Foster said the two biggest challenges with blindside waterproofing are quality assurance – “We conduct site reviews to ensure the waterproofing applications are all done by third parties according to specifications” – and ensuring building trades working on the site don’t damage the membrane. 

Foster cited several examples of the challenges associated with high worker traffic around the installation of blindside waterproofing:

  • Because a drain was missed the first time, installers cut a hole in the waterproofing, but the penetration wasn’t detailed.
  • When the rebar trade installed the cage for the shotcrete application, it inadvertently punched holes in the membrane, which damaged its integrity.
  • Someone accidentally kicked a detailed pipe penetration for a tanking application but neglected to tell the rest of the team on the worksite.

Foster said blindside waterproofing is used on new institutional, commercial, mixed-use and bored rock tunnel applications.

ESP Engineered Site Products handles three types of blindside waterproofing products: bentonite geotextiles; bentonite and active polymer core embedded geotextile membrane; and thermoplastic polyvinyl chloride (PVC) membrane with an active polymer core.

ESP Engineered Site Products is a supplier of CETCO (Colloid Environmental Technologies Company) waterproofing materials in a sales territory that extends from B.C. to Manitoba.

CETCO, for its part, is a subsidiary and construction technologies business unit of Minerals Technologies Incorporated, which calls itself the world’s largest bentonite mining company. 

Bentonite is an absorbent swelling clay that is the product of the weathering of volcanic ash in seawater.

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