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CERESIT BT 21 Sealing membrane

  • Immediately water- and rain resistant
  • Cold-applied
  • Flexible and crack-bridging

Features and benefits

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

Properties

Description

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.

Documents and downloads

How to use

SUBSTRATE PREPARATION FOR APPLICATION OF CERESIT BT 21

Before installing the BT 21 waterproofing membrane, all mineral substrates must be pretreated with a BT primer. At temperatures above +5 °C, use BT 26 "AllWeather" Primer, at lower temperatures use BT 28 Special Primer (solvent-based).

APPLICATION OF CERESIT BT 21

Slowly and uniformly peel approx. 1 m backing paper off the strip's top edge. Align the strip and fix it to the substrate with the adhesive side down. Continue to peel off the paper and to bond the remaining part of the strip. After that, press the entire strip firmly down, e.g. with a rubber roller. 

IMPORTANT TO NOTE WHEN USING CERESIT BT 21

Use the BT 21 »All-Weather« Waterproofing Membrane only in dry conditions at temperatures from –5 °C to +30 °C (but not in blazing sunshine) and below 80 % relative air humidity. 

Related how to guides

  • Horizontal barrier under foundation wall
  • Concrete structures protection with mineral waterproofing slurries

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Frequently asked questions