Internal tanking is the provision of a waterproof internal tanking membrane to the inside of the basement or sub-structure in accordance with BS8102:2009 (Type A - Barrier protection). When selecting a suitable internal tanking membrane system, consideration should be given to the form of construction, ground water levels, ground drainage, soil type and ground contamination.
When internal basement tanking with applied membranes, you must allow for hydrostatic pressure acting upon the membrane, and therefore a ‘loading coat’ may be required, unless a product from our cement range is used.. Sub-soil drainage systems should also be incorporated into the design, when required.
In areas where the water table is classed as “High”, combined protection is recommended; please consult the RIW Technical Department.
RIW LAC, a two coat bitumen solution is BBA approved as an internal 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 can also be used as an internal 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 Cavity Drain is another type of system used to internally protect basements, ie: (Type C - Drained protection) - See also “Cavity Drainage Systems”.
The system is a HDPE profiled sheet, which is mechanically fixed to the walls, and laid on the slab under suitable finishes. The RIW Cavity Drain will allow water to pass through the retaining wall, into the cavity former, where it is channelled to a sump with a pump or other suitable drainage outlet. This system does not require a ‘loading coat’ to the vertical surface. It is suitable for use if the water table is high, and does not require additional external land drainage. Also surface preparation is far less critical than the requirements for applied membranes.
RIW Toughseal can be used internally below ground level in conjunction with other forms of waterproofing. Please consult the RIW Technical Department for site specific advice.
RIW Cementseal and RIW Cementflex, both high performance cement based coatings, are suitable for use as internal tanking membranes that will resist up to100m head of negative water pressure without the need for a loading coat. This is particularly beneficial in small basement tanking or refurbishment & works.
RIW Cementfill FC and RIW Cementfill HB repair mortars are also available to assist with the substrate preparation.
(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 internal tanking and basement tanking please contact the RIW Technical Department.