Features and Benefits

Bitumen-rubber emulsion used for priming self-adhesive membranes, sealing strips and fixing tapes.


  • For application temperatures down to -5 °C
  • Also suitable for damp and cold surfaces
  • Rapidly-drying 
  • Low-odour
  • Indoor and outdoor use
  • Amount required (depending on type of use); approximately 150 to 300 g concentrate/m2

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CERESIT BT 26 is a high-quality, water-dilutable bitumen-rubber primer used to improve the adhesion of sealing membranes and strips. It can be applied on all absorbent mineral substrates, e.g. concrete, plaster, foam concrete, sand-lime or brick masonry with a level surface, weather-worn bituminous surfaces, rigid foam boards made of extruded polystyrene and on the non- woven backing of the CA 22 fixing tape in the overlap area.

Step by step

Substrate preparation


Use Ceresit BT 26 »All-Weather« Primer only on level, solid, load-bearing, clean, dry or slightly damp substrates. Brush off the existing load-bearing bituminous substratesand free them from dust. Very thoroughly free the foundation base projection and the base slab front from dirt and excess mortar. At low temperatures make sure that the substrate is free of ice.



Before use, mix Ceresit BT 26 »All-Weather« Primer carefully with water at a ratio of 1 : 1 parts by volume. Use an electric drill with stirrer attachment. The diluted primer can be used at temperatures down to +5 °C. At lower temperatures (down to 0 °C), use BT 26 undiluted. In the case of coarse-pored surfaces, e.g. pumice and hollow blocks as well as aerated concrete, the primer must always be used undiluted. Use a ceiling brush to apply a generous and uniform coat. BT 26 is also suitable for machine application with airless spray guns. Please contact us for recommendable spray guns. Before installing the BT 21 »All-Weather« Waterproofing Membrane, make sure the priming coat has completely dried. Always check whether there is sufficient adhesion to the surface. For this purpose, place a strip of BT 21 (approx. 5 x 10 cm) on the primed surface, press home and strip off again. If more than 30 % of the priming coat comes off, it has not yet dried sufficiently. Through-drying times depend on the site-specific conditions, e.g. surface moisture, relative air humidity and temperature. Please refer to the "Technical Data" for approximate drying times. Remove excess primer with water while the material is still fresh.