Tanking is defined as a waterproof membrane applied over a surface, preventing completely the entry of liquid water under hydrostatic (water) pressure. External tanking is usually undertaken using a sheet membrane system although various options are available. The waterproofing of retaining walls on single-sided basements, sloping sites or step changes in modular floor construction are amongst the most common works undertaken by Siteseal.

The current Building Regulations and BS 8102:1990 (Protection of structures from ground water), stress the importance of, where possible,

(i) maintaining the continuity of the waterproofing system,
(ii) avoiding breaking the integrity of the waterproofing with wall ties and
(iii) the desirability of cross flow ventilation.

The optimum remedy will depend on a host of factors such as, age of the building (existing buildings only), proximity to any water courses or ground water, the level of waterborne contaminants, condition of the existing masonry or brickwork and nature of the water ingress.

External Coatings: Applied to the to external face of brick, stone or concrete structures these work by lining the pores of the masonry rather than blocking them - allowing the wall to continue to breathe, whilst preventing water ingress.