Cavity Drainage Systems
A cavity drainage system within the basement or sub-structure is the provision of a continuous pre-formed cavity, which intercepts and drains away incoming water in accordance with BS8102:2009 (Type C - Drained protection). There is a permanent reliance on this cavity to collect groundwater seepage through the structure and channel it to drains or a sump for removal by drainage or pumping. When selecting a suitable drainage cavity system the external basement structure must provide enough resistance to water ingress to ensure the cavity only accepts a controlled amount of water. When specifying a cavity drainage system, due consideration should also be given to the form of construction, ground water levels, external ground drainage, soil type and ground contamination.
RIW Cavity Drain is a profiled HDPE sheet cavity former that provides a clear and safe route for water seepage into an existing or new basement. It will also provide the all important vapour barrier to enable this low risk form of construction (BS8102, type C) to be used for all basement usage without ventilating the cavity. RIW Cavity Drain is usually installed as art of a cavity drainage system inside the basement structure and onto the structural slab. Facilities for draining ground water ingress must be incorporated into the design and this can involve casting the structural slab to falls to direct water to pumped collection sumps and/or to a gravity fed drainage system. Two sizes of RIW Cavity Drain are available (20mm and 5 mm) and selection depends upon type of construction, ground conditions and expected quantity of water ingress. The 20mm system is always used for horizontal work, with the 5mm system being used vertically if suitable.
RIW Plaster Drain, works on the same principle as RIW Cavity Drain but incorporates a surface designed to support plaster or render finishes. It is usually used where internal space is at a premium and where a low level of water ingress is envisaged. It can also be used as part of a cavity drainage system vertically to damp walls above ground, where it can be ventilated top and bottom, as well as in conjunction with the larger RIW Cavity Drain membrane on the floor.
(Identify the most appropriate RIW product(s) for your specific application from the text above and click on the product icon on the right to access the product page for more information and downloadable data sheets).
For more information about Cavity Drainage Systems please contact the RIW Technical Department.