Volclay Waterstop RX

RX 101 Box
RX 101 product
RX 101T Box
RX 101T product
RX 102 Box
RX 102 product

Waterstop-RX is an active bentonite/butyl-rubber based waterstop designed to stop water infiltration through cast-in-place concrete construction joints by expanding upon contact with water to form a positive seal against the concrete. 

The key to the effectiveness of Waterstop-RX is it’s 75% sodium bentonite content which provides superior expansion to seal cracks and fill small voids. Waterstop-RX is a reliable and cost-effective solution to preventing water infiltration through concrete joints. 

Waterstop-RX offers a low cost opportunity to enhance the performance of a sound external waterproofing system, by sealing the areas of highest probability of water infiltration through the concrete, and should therefore be implemented as part of the waterproofing design.

Waterstop-RX can also be refereed to as a swellable water bar when being used in projects involving new to old slabs joins.

Three different sizes and profiles are available to match to your specific project needs: RX-101, RX-101T, and RX-102.

  • Waterstop-RX 101 is the largest profile with a rectangular cross section of 25 x 19 mm. Requiring only 75 mm of concrete coverage. Roll length 5Lm per roll.
  • Waterstop-RX 101T is a 31 x 12 mm trapezoidal shape profile. The patented trapezoidal shape of RX-101T distributes the expansion pressures over a greater area and the reinforcing scrim provides additional product stability when concrete is placed. Requiring only 75 mm of concrete coverage.  Roll length 6.10Lm per roll.
  • Waterstop-RX 102 is a half-round profile measuring 19 x 9 mm. Requiring only 50 mm of concrete coverage.  Roll length 10.2Lm per roll.
  • Easy to Install – Waterstop-RX can be installed by one person 
  • Positive Seal – Waterstop-RX swells and forms a positive seal.
  • No Special Transition Parts – Waterstop-RX does not require special cross, corner, or “L” parts to transition from horizontal to vertical.
  • Safe – Waterstop-RX is non-toxic and requires no special handling.
  • Flexible – Waterstop-RX has excellent flexibility so it can be installed around irregular penetrations like steel H-Piles.
  • New-to-existing Concrete – Installs without chipping or saw-cutting existing concrete
  • durability
  • externalMoisture
  • appraised
  • bba appraised

APPLICATIONS: Applications include both vertical and horizontal non-moving concrete construction joints, new to existing concrete construction, irregular surfaces, and around through-wall penetrations, such as plumbing and utility pipes. Additionally Waterstop-RX can seal around concrete pilings and steel H-piles passing through the slab. Waterstop-RX works in both continuous hydro-static and intermittent hydro-static conditions

B2 DURABILITY: Performance B2.3.1 (a) not less than 50 years. 
E2 EXTERNAL MOISTURE: Performance E2.3.3. 
F2 HAZARDOUS BUILDING MATERIALS: Performance F2.3.1. The Volclay Waterproofing System meets this requirement and will not present a health hazard to people.
BRANZ and BBA Appraised


  • Waterstop-RX is not a self-adhering product. CETSEAL or Masonry Nails are required to secure Waterstop-RX to concrete, metal, or PVC (Pipe) surfaces (fasteners can be used in conjunction with CETSEAL).
  • Waterstop-RX is not designed, nor intended to function as an expansion joint sealant. For precast concrete applications, contact manufacturer for product suitability and for any special installation requirements. Waterstop-RX products are designed for structural concrete with a minimum of 20N/mm2 3,000 psi compressive strength.
  • Waterstop-RX 101 and RX-101T require a minimum of 75 mm (3”) of concrete coverage.
  • Waterstop-RX 102 requires a minimum concrete coverage of 50 mm (2”).
  • Waterstop-RX should not be pre-hydrated by being subjected to submersion or remain in extended contact with water prior to encapsulation in concrete.  
  • In conditions where severe ground water chemical contamination exists, or is expected, consult Allco for product chemical compatibility information


  • Waterstop-RX 101 is supplied in 5mtr rolls / 6 rolls to a carton
  • Waterstop-RX 101T is supplied in 6.10mtr rolls / 6 rolls to a carton
  • Waterstop-RX 102 is supplied in 10.2mtr rolls / 6 rolls to a carton

 For further product information please see our frequently asked questions 

WQIP Building

Due to the location of the building in the Wynyard Quarter there is a high concentration of contaminants, high water table and saline. A waterproofing membrane was required not only to handle hydrostatic pressure but also to act as a vapour barrier protecting indoor air from potential ingress of hydrocarbon vapours.

Harewood Underpass

Another watertight underpass is completed. The brief was durability for the life of the structure with a requirement to be leak free to maintain the integrity of both the profiled panel façades and the Architectural Coating.

Auckland Art Gallery

The project involved a significant amount of civil works, with retention piling, soil nails and ground anchors used to allow excavation and construction of new basement levels between the heritage buildings. Because it was built into the side of a hill, high hydrostatic pressure was constantly present.

The Hills Golf Club

The self-sealing properties of the Volclay Swelltite Sodium Bentonite Membrane made an ideal choice for this & other high profile earth covered structures.  With the minimum confinement criteria of 300mm earth cover (over the Swelltite) achieved; this application was very straight forward and has gone on to showcase in several...

Auckland War Memorial Museum

The rear Southern courtyard, built in 1960, provided the space for six new floors. The courtyard was excavated to a depth of 12 metres to allow two basement levels. Above ground, four new levels were contained in a ‘bowl’ structure and topped by a copper and glass dome.

Vodafone Building

The basement parking areas for the building were below sea level and the structure was located close to the boundaries. The site was on reclaimed land within 10m of Waitemata Harbour and the site was contaminated with various oils, petro chemicals & saline.

St Mary’s College

Tanking to footings and precast panel retaining walls, lift pit and storage areas, plaza deck, roof and gutters

Rose Garden Apartments

Tanking to footings and precast panel retaining walls, AFS walls, lift pit and storage areas, plaza deck, roof and gutters.

Westpac Charter House

The building of the three level basements required excavation down to 11 metres below street level and eight metres below sea level. The site is on reclaimed land. Ground contamination from its former use as a petrol station was mitigated with the introduction of sediment control and filter pumping systems...

The Sentinel Apartments

As the plaza deck waterproofing was to be staged over a number of months with tight construction deadlines a membrane that was able to placed and detailed in virtually any weather was a must. The membrane was also required to be tough and self healing if damaged by construction site...


Volclay - BRANZ Appraisal

Volclay Waterstop RX - Product Manual

Volclay Waterstop RX - Product Brochure

Volclay Waterstop RX - Tech Data

Volclay Waterstop RX - BBA Appraisal

Volclay Waterstop RX - Checklist

Volclay Waterstop RX - BBA Approval