Features and Benefits

Self-adhesive membrane for reliable waterproofing of buildings in the temperatures above 5 °C


  • Immediately water- and rain resistant
  • Cold-applied
  • Flexible and crack-bridging
  • In combination with BT 26 applicable also on moist surfaces
  • Amount required: 1.08 m2/m2

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Ceresit BT 21 is used for sealing vertical and horizontal surfaces of buildings, structural components and below the ground structures, such as underground car parks and subways. It is suitable for waterproofing basement walls, garage roofs, balconies, terraces, wet rooms and patios. Also used as a sealant against capillary rise of moisture and as a water vapour barrier in floor areas under screeds. Ceresit BT 21 can be applied on smooth, cavity-free surfaces such as concrete, screeds, plasters, bitumen, wood, metals, ceramic tiles and thermal insulation (PUR, ESP). In combination with BT primers it can also be applied on moist and old surfaces down to -5 °C. Tested at the German Institute of Construction Engineering

Step by step

Substrate preparation and application of membranes need to be treated very carefully because any wrong usage of these products could cause serious damage.Therefore, regarding all information please check thoroughly TDS (technical data sheet).