Avon & Somerset Police HQ RIW Case Study

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1 Avon & Somerset Police HQ Design should be considered at an early stage The new headquarters completed for the Avon & Somerset Police in Portishead is a typical example of the importance of considering waterproofing at an early stage in new building design. RIW were contacted by Bruges Tozer to put forward their recommendations for damp proofing the ground floor slabs of the HQ building. The installation was particularly interesting as the architect wanted to achieve a simple and uniform installation without altering the waterproofing needed for the varying conditions. The different elements that needed to be waterproofed included ground floors with finishes ranging from carpet to vinyl, computer rooms with raised access flooring and a lecture theatre below ground level requiring tanking. RIW Toughseal was applied in situations where the traditional method of using a screed to protect the waterproof membrane could not be used. In areas where raised access floors were required the pedestals were adhered directly to the membrane avoiding the need for mechanical fixings and the inherent danger of penetrating the membrane. Where suspended wood flooring on wood battens was specified, the membrane was applied to the concrete floor slab, enabling the battens to be fixed directly to the slab. In both of these situations the elimination of a screed provided benefits in terms of cost and time while allowing the continuity of the membrane to be unaffected. The ground floor also included pre-cast plank construction. In this situation, movement between individual components was considered a possibility. To overcome this, RIW s Flexiseal was specified. Flexiseal is a rubber-like flexible liquid membrane which can accommodate up to 4-5mm of movement without failure of the membrane. In more traditional situations where a screed was provided, RIW LAC was used as the damp proof membrane. At all stages care was taken to ensure that continuity of the membranes was achieved despite the differing construction techniques and finished flooring requirements. The nature of the construction programme required RIW s technical staff to respond very quickly to the requests for details with information being faxed between the two companies. RIW also checked all specifications and visited the site to ensure the products were being applied correctly. CS.01 RIW Toughseal Two coat, highly durable waterproof membrane based on epoxy resins Raised access floors Plant rooms / bunded areas Wet areas Surface membrane (DPM) RIW Flexiseal Two coat, flexible, seamless and fully bonded waterproof membrane based on Polyurethane resins Basement tanking Deck areas Balconies / terraces Ground floor DPM RIW LAC Two coat, seamless and fully bonded waterproof bitumen solution Ground Floor DPM Basement Tanking Superstructures Professional technical advisory helpline Standard & site specific specification Standard & site specific method statements Interactive website

2 Sharkham Village Development Sept 2006 CS.02 Millwood Homes (Devon) Ltd, a developer from Newton Abbot, sought advice from RIW on how best to protect a proposed development in Brixham against water ingress and Radon emissions. THE PROBLEM The Sharkham Village development was to be constructed on a sloping site and consisted of a number of new town houses that stepped up a slope thus creating a series of single-sided basements. As the development steps up the hill a suspended beam & block floor was selected rather than a ground bearing slab. Millwood Homes were keen to develop a tanking detail that would conform to the Building Regulations and provide adequate protection against the potential for ingress of water and radon emissions. Whilst liaising with Millwood Homes, RIW understood that the proposed detail not only needed to prevent the ingress of water, water vapour and Radon but that it also needed to be as simple as possible to install on site due to the consequences should the waterproofing prove inadequate. If possible, the proposed detail should avoid sequencing problems to avoid unnecessary delays to the construction programme. THE SOLUTION RIW s Technical Department proposed the use of RIW Cavity Drain (as shown overleaf) which can be linked into the DPM with RIW Sheetseal 9000 DPC. This detail ensures continuity between each element of the waterproofing design and encourages cross ventilation through the cavity to ensure the Radon emissions disperse freely. The use of RIW Cavity Drain vertically also eliminates any direct water pressure allowing water that passes through the vertical structure to drain freely into the void under the block & beam floor. Also if wall ties are required to tie back the internal masonry wall, they can be screwed into the brick plugs used to fix the Cavity Drain system, thus avoiding the necessity to puncture the membrane and break the waterproofing/radon integrity. Nigel White of Millwood Homes said We wanted a solution that was straight forward to build and would not delay progress on site, but we didn t want to have separate waterproofing and Radon barriers. We initially considered an external tanking system but this could not easily be linked to the Radon barrier. We were therefore very pleased when we contacted RIW and they suggested the Cavity Drain system. This resolved all the problems and allowed progress to continue unhindered on site as all the tanking could be installed after the in-situ concrete foundations and retaining walls had been constructed. RIW Cavity Drain High density polyethylene drain board with 20mm studs used in situations where site conditions or structural design make it difficult or impossible to use traditional tanking methods. Basements Retaining walls RIW Sheetseal 9000 DPC High quality polymeric DPC based on a composition of Ethylene Propylene rubbers and polyester fibres which increase the tensile strength and elongation at break making the system more resistant to tearing and puncturing. Horizontal bed joints Vertical jamb DPC Horizontal cavity trays Lintel trays Sill trays Parapet trays Professional technical advisory helpline Standard & site specific specification Standard & site specific method statements Interactive website

3 Sept 2006 CS.02 DRAWING No. SD / TYPICAL / 007 RIW Limited Arc House, Terrace Road South Binfield, Bracknell Berkshire RG42 4PZ DATE: FEB 2006 DRAWN BY: MR SCALE: NTS CHECKED BY: MJA STANDARD DETAIL: RETAINING WALL DETAIL WHERE RADON IS PRESENT TYPICAL RETAINING WALL DETAIL TO ENCOURAGE CROSS VENTILATION OF A CAVITY USING RIW CAVITY DRAIN

4 Wandsworth Southside Shopping Centre November 2006 CS.03 The form of construction, substrate profiles and preparation all influence the selection and ultimately the success of a waterproofing system. 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 or 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 Composite of high swelling Sodium Bentonite encapsulated between a non-woven and woven geotextile. When wetted, unconfined Bentonite can swell up to 15 times its dry volume. When confined under pressure within a structure the swelling is controlled, forming a dense, monolithic, impervious waterproofing membrane. Typical Uses Basement tanking Boundary line construction Retaining walls Under slab ground floor DPM Features & Benefits Two coat, seamless and fully bonded waterproof bitumen solution Quick & easy to install Pre-applied tanking system Self-sealing properties Factory controlled thickness Suitable for wet weather applications Unaffected by low temperature No extensive surface preparation required Resistant to 70m head of hydrostatic pressure Ancillary Products RIW Waterstop RIW Sealing Compound RIW Granules

5 Wandsworth Southside Shopping Centre November 2006 CS.03 Structureseal is the most user friendly and forgiving membrane in the RIW range of high waterproofing systems. RIW Structureseal, a highly effective waterproofing composite of high strength green coloured geotextile and high swelling sodium bentonite, was presented to Leslie Jones Architects as the most appropriate waterproofing system to use on this site. The attributes and limitations of the system match many of their requirements. In fact, RIW Structureseal is the most user friendly and forgiving membrane in the RIW range of high 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 shown in the typical pile cap detail shown. As a pre-formed 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, Typical RIW Structureseal application after the formwork has been removed. The 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. Professional Helpline Standard & site specific specifications Standard & site specific Method Statements Comprehensive, interactive website offering downloadable data sheets and standard drawings