November 2006

RIW Limited was called in by Leslie Jones Architects to advise on the waterproofing strategy for the basement sub-structure of the £70m refurbishment of Wandsworth Southside Shopping Centre.

The scheme involved demolishing one third of the existing centre to provide the new anchor footprints and to meet the improved car parking requirements. The new centre included tenants such as Waitrose, Cine UK & Virgin Active.

THE PROBLEM

The form of construction; reinforced concrete sub-structure constructed on a network of pile caps and ground beams, created complicated waterproofing details which were difficult to install. In addition, the site was very wet during the installation of the waterproofing, and required de-watering during the construction phase.

The form of construction, substrate profiles and preparation all influenced the selection and ultimately the success of the waterproofing system.

Some areas of the existing building formed the boundary line for the new sub-structure. Waterproofing against site boundary lines can prove difficult and complex for traditional waterproofing systems as they generally provide irregular substrates and little or no working space which limits the waterproofing options.

Unless installed by a specialist, traditional waterproofing systems such as liquid applied or self adhesive sheet membranes are vulnerable to poor workmanship when applied on such complicated forms of construction. Generally, they also need to be applied to a dry substrate, which can be difficult to achieve on some sites.

THE SOLUTION

RIW Technical Advisor John Clucas visited Leslie Jones to discuss the waterproofing strategy for the project. It soon became apparent that the most appropriate waterproofing system must have the following key attributes: 

• Quick and easy to apply to irregular / complex substrates
• Suitable for wet weather & low temperature applications
• Suitable for installation onto wet substrates
• Suitable to be pre-applied to boundary line construction
• Resistant to damage from concrete placement and following trades
• Leslie Jones requested a BBA approved system

RIW Structureseal, a highly effective waterproofing composite, of high strength green coloured geotextile, and high swelling sodium bentonite, was presented to Leslie Jones as the most appropriate waterproofing system to use on this site. The attributes and limitations of the system match many of the requirements outlined above.

In fact, RIW Structureseal is the most user friendly and forgiving membrane in the RIW range of high performance waterproofing systems.

When wetted, unconfined bentonite can swell up to 15 times its dry volume. When confined under pressure the swell is controlled, forming a dense, monolithic, impervious waterproofing membrane.

The swelling action of RIW Structureseal can self-seal small concrete cracks caused by ground settlement and concrete shrinkage.

These self-sealing qualities ensure that RIW Structureseal, when used in conjunction with RIW Sealing Compound, is easily detailed around complex substrate profiles.

As a preformed membrane that actively seeks as well as prevents the transmission of water, the membrane can be laid directly on to well compacted ground that is wet. It is also unaffected by rain prior to the placement of the concrete, provided it isn’t immersed in standing water for long periods. These features allow the system to be applied in all weather conditions having a positive effect on the contractor’s program.

As a pre-applied membrane, it can be mechanically fixed to most vertical substrates even when working against the boundary line. The concrete can be placed directly against the RIW Structureseal without the need for additional protection. The geo-textile fibres will be trapped in the wet concrete, and allow the RIW Structureseal to remain firmly attached (peel adhered) to the concrete, after the formwork has been removed.

RIW Structureseal is complemented by a number of ancillary products that complete the waterproofing system, including RIW Waterstop which is used in all concrete construction joints within the reinforced concrete.

RIW Structureseal has been awarded a British Board of Agrément certificate, number 02/3953.

RIW Structureseal has proven to be the right product specification for this project and supported by the RIW Technical expertise the installation was completed successfully, fully meeting Leslie Jones Architects expectations.

Jennifer Boyce of Leslie Jones Architects commented, “We can confirm our satisfaction with this product and will continue to specify it following its proven robustness of installation, reliability in waterproofing and compatibility with other DPM systems”.

PROJECT DETAILS
Project Name: Wandsworth Southside Shopping Centre
Architect: Leslie Jones Architects, London
Installer: FDL, Wallington, Surrey

Products used: RIW Structureseal
RIW Sealing Compound
RIW Granules
RIW Waterstop

Date: Oct 2002 – Nov 2003