External Tanking

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.

Works can be carried out in different ways to ensure a waterproofed/dry space, a Cemplas diagnostic survey will identify the prevalent factors and take into account the causes of water ingress.

Waterproofing of retaining walls on single-sided basements, sloping sites or step changes in modular floor construction is a perennial problem.

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.

When the membrane is applied to the external walls of the basement structure, the “base / site slab” of un-reinforced site concrete should extend for at least 300 mm beyond the outer face of the basement wall. The horizontal membrane is laid to the base slab, the membrane applied to cover the full base slab. A sand cement screed or protection boards are then applied over the membrane depending on site conditions, ensuring the membrane is not damaged during assembly of the reinforcing steel rods of the loading / finished slab.

Cemplas understands that the optimum remedy will depend on a host of factors such as the: age of the building (existing buildings only) proximity to water courses level of waterborne contaminants condition of the existing masonry or brickwork nature of the water ingress.

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