Nusite Group installs bentonite waterproofing systems on commercial, institutional and infrastructure projects across the GTA and Southern Ontario. Established in 1990, we work within larger project teams on blindside and pre-applied below-grade scopes, where the membrane is installed against shoring before the structure is poured and there is no second opportunity to correct the detailing.
Bentonite is specified where conventional post-applied membranes cannot be installed — zero lot line excavations, shoring walls, under-slab applications, and deep below-grade structures under sustained groundwater pressure. These are sequencing-critical scopes. The membrane goes in ahead of reinforcing and concrete placement, is inspected before the pour, and is permanently inaccessible afterwards.
How Bentonite Systems Work
Sodium bentonite swells on contact with water, expanding into a dense, low-permeability gel that seals against the structure. Unlike a liquid-applied or sheet membrane that forms a static barrier, bentonite responds to water by closing the path it travels through, which allows it to self-seal minor defects and conform to irregular substrates.
The property that makes it work is also its principal constraint. Bentonite requires confinement to perform: the swelling clay must be held between the structure and the soil or shoring. Unconfined, it swells and migrates rather than forming a barrier.
For a fuller explanation of the material itself, see What Is Bentonite Waterproofing And When Is It Used?
Manufacturer Systems
Nusite Group is a certified installer for Carlisle and Tremco systems. Both manufacturers produce below-grade bentonite composites specified on commercial projects in this market. System selection follows the project specification, the water conditions and the construction sequence.
Tremco Paraseal combines HDPE with granular bentonite. Paraseal GM/LG 20 Mil is a three-layer construction — 20 mil HDPE, expandable granular bentonite, and a spun-bonded polyester protective layer — with the HDPE extending past the bentonite at the perimeter edges to give a clean surface for seam tape. The bentonite expands up to eight times its original thickness on hydration. Paraseal LG is the variant specified for backfilled wall conditions.
| Property | Result | Standard |
|---|---|---|
| HDPE thickness | 20 mil | — |
| Elongation | 500% | ASTM D412 |
| Resistance to hydrostatic head | 231 ft of water | ASTM D5385 |
| Application temperature | −25°F to 130°F (−32°C to 54°C) | — |
| Bentonite expansion | Up to 8× original thickness | — |
| Hydrocarbon resistance | Yes | — |
Published applications include blindside walls, below-slab-on-grade, methane mitigation, damp and green concrete, and submerged conditions.
Carlisle MiraCLAY is a geotextile panel carrying sodium bentonite between woven and non-woven puncture-resistant polypropylene layers, thermally bonded so the clay stays distributed regardless of incline or repeated hydration cycling. It is used for pre-applied below-grade work, foundation walls and under-slab applications, and may also be used post-applied on foundation walls. The manufacturer cites cold-weather suitability, self-sealing and puncture resistance, application over green concrete, and earlier form removal than adhesive-bonded systems.
Figures above are published manufacturer data describing tested product performance, not performance criteria for installed conditions. Confirm the current data sheet for the specified system on any project.
Where Bentonite Is Specified
- Blindside walls against shoring, soldier pile and lagging, or an adjacent structure
- Zero lot line excavations where no exterior access will ever exist
- Under-slab waterproofing beneath structural slabs and mat foundations
- Elevator pits and other deep below-grade elements
- Underground parking structures and multi-level below-grade construction
- Foundation walls where the membrane can be properly confined by backfill
- Methane and vapour mitigation, where the specified system is rated for it
Across all of these, the common condition is that the exterior face of the waterproofing becomes permanently inaccessible once construction proceeds.
Detailing and Sequencing
Bentonite systems fail at details, not in the field of the membrane.
Seams and overlaps. Laps detailed to the manufacturer’s requirement, with seam tape applied to a clean surface.
Tiebacks and penetrations. Shoring tiebacks, pile caps, service penetrations and form ties each require a specific detail. These are the highest-risk locations on a blindside scope.
Transitions. Slab-to-wall and horizontal-to-vertical transitions, and tie-ins to adjacent waterproofing systems where assemblies change.
Protection before the pour. The membrane is exposed to reinforcing steel placement, foot traffic and weather between installation and concrete placement. Protection and pre-pour inspection are part of the scope, not an afterthought.
Premature hydration. Bentonite that wets and swells before the structure is cast may not perform as intended. Sequencing and weather protection matter.
Coordination. On a blindside scope the waterproofing contractor works between the excavation, shoring, forming and reinforcing trades. Schedule integration is as much of the scope as the installation.
When Bentonite Is Not the Right System
A contractor who installs one system will specify it everywhere. The conditions where bentonite is the wrong answer:
- No confinement. If the membrane cannot be held between the structure and the soil or shoring, it will not form a reliable barrier.
- Retrofitting an existing structure from the inside. Bentonite is a pre-applied, backfilled system. Remediating an existing below-grade leak generally calls for injection or a negative-side system instead.
- Unusual groundwater chemistry. Saline or highly mineralised groundwater can reduce swelling performance depending on the product. Where this is a known site condition, confirm the manufacturer’s data.
- Hydrostatic pressure beyond the system’s rating. Verify the tested limit against the design head rather than assuming all bentonite products perform alike.
- Structural defects. Bentonite seals minor imperfections. It does not substitute for repairing significant cracks or structural deficiencies.
Nusite Group installs open cut, blindside, sheet and spray-applied, crystalline, cementitious and injection systems — which means the recommendation reflects the condition, not the inventory.
Working With Nusite Group
Nusite Group is a commercial specialty contractor established in 1990, delivering waterproofing systems, concrete and structural rehabilitation, and commercial roofing for institutional, industrial and complex commercial buildings across the GTA and Southern Ontario.
We support blindside and bentonite scopes from preconstruction onward — system selection, constructability review, detailing input and budget planning — and coordinate installation within the general contractor’s sequence.
- Established 1990
- Fully bonded contractor
- Licensed across Ontario
- $10 million liability coverage
- Certified installer for Carlisle and Tremco systems
- Preconstruction support and design-assist
Request a system review, or invite Nusite Group to bid your below-grade waterproofing scope. Discuss your project with Nusite Group.
Frequently Asked Questions
Does Nusite Group install bentonite waterproofing on commercial projects in Toronto?
Yes. Nusite Group installs bentonite waterproofing systems on commercial, institutional and infrastructure projects throughout the GTA and Southern Ontario, including blindside, under-slab and foundation wall applications.
Which bentonite systems do you work with?
Nusite Group is a certified installer for Carlisle and Tremco systems, both of which produce below-grade bentonite composites. System selection follows the project specification, the water conditions and the construction sequence.
What is blindside waterproofing and how does bentonite apply to it?
Blindside waterproofing is installed against shoring or an adjacent structure before the concrete is placed, because the exterior face will never be accessible. Bentonite composites are commonly specified for this condition.
How much hydrostatic pressure can bentonite waterproofing withstand?
It depends on the system. Tremco Paraseal GM/LG 20 Mil is published at 231 feet of hydrostatic head, tested to ASTM D5385. The design head should always be checked against the specific product’s tested limit.
Can bentonite waterproofing be installed in cold weather?
These systems carry wide application temperature ranges, and Paraseal GM/LG 20 Mil is published from minus 25 to 130 degrees Fahrenheit. They can also be applied over damp or green concrete. Protection from premature hydration remains a sequencing requirement.
Can bentonite be used to repair an existing below-grade leak?
Generally no. Bentonite is a pre-applied, confined system installed before the structure is cast. Remediating an existing below-grade leak usually calls for injection or a negative-side system instead.
What areas does Nusite Group serve?
Nusite Group serves the Greater Toronto Area and Southern Ontario.
