External Tanking

External tanking is the provision of an external tanking membrane to the outside of the basement or sub-structure in accordance with BS8102:2009 (Type A - Barrier protection). When selecting a suitable external tanking membrane system, consideration should be given to the form of construction, ground water levels, ground drainage, soil type and ground contamination.

Generally, waterproof external tanking membranes are installed onto a horizontal blinding and vertically to reinforced concrete or masonry sub-structures. Boundary line construction applications, including secant piling, contiguous piling and sheet piling, create challenging substrates and therefore some waterproof wall tanking membranes will not be deemed suitable, due to factors such as the need for excessive surface preparation. Sub-soil drainage systems should be incorporated into the design, when required.

In areas where the water table is classed as “High”, combined protection is required, please consult the RIW Technical Department.

RIW LAC, a two coat bitumen solution, is BBA approved as an external tanking membrane, and has been used as such for over 90 years. However, RIW Flexiseal is a high performance alternative, with its colour coded quality control system and excellent flexibility making it especially suitable for masonry structures.

RIW Sheetseal 226 is also widely used as a horizontal external tanking membrane. Large areas may be applied quickly with no drying time, especially to horizontal surfaces. Using a combination of membranes, for instance, RIW Sheetseal 226 horizontally and RIW Flexiseal vertically, should always be considered to achieve the ideal design.

RIW Structureseal is a pre-applied system used in boundary line construction applications including secant piling, contiguous piling, sheet piling. RIW Structreseal is ideal for challenging site applications, and where other systems may not be deemed suitable due external factors such as accessibility, site geology or inclement weather.

RIW Waterstop should be incorporated in all construction joints in reinforced concrete sub-structures.

RIW Cementfill  repair mortars are available to assist with the substrate preparation.

RIW Double Drain is available to relieve hydrostatic pressure build-up.

(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 on external tanking and wall tanking please contact the RIW Technical Department.