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Last edited 16 May 2019
Tanking is a term used for creating a tank-like seal to protect walls against water penetration. The Building Regulations stipulate that tanking must be applied to all new build structures below ground, but tanking can also be applied to existing buildings, to prevent water penetration into basements and cellars, as well as helping to tackle rising damp.
The two main methods of tanking are by using a membrane or a coating. The type of damp and the precise requirements of the building will determine the most appropriate method to use, and sometimes a combination is required to ensure walls remain dry.
 Tanking membranes
The studs create an air gap cavity between the wall and membrane. Where there is no visible water in the cavity, ventilation may be adequate to prevent the accumulation of moisture. Where water is present, drainage or a or sump and pump may be necessary.
Liquid bitumen is painted onto cleaned masonry or render but is best for smaller jobs or for coating externally below the damp-proof course. It can prove difficult to apply to masonry in older buildings as it can separate from the wall if applied incorrectly.
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