Köster 21


Two component, solvent free, liquid applied, elastic, crack bridging waterproofing material with excellent adhesion to dry and moist substrates. Being liquid applied it is seamless, which greatly eases application to complicated architectural details.

Due to its UV stability it is suitable for indoor and outdoor use. The white colour reflects sunlight and reduces building surface temperatures. Contains no volatile organic compounds (VOC) and is free from polyurethanes, isocyanates and bitumen.

The fast curing coating is highly flexible, resistance to occasional foot traffic, aging, hydrolysis, UV rays, frost and salt. Can seal against synthetic oils and aliphatic hydrocarbons with high boiling points.

Not resistant against substrates with high aromatic hydrocarbon contents such as benzene, xylene, toluene, etc.

Suitable for use as a waterproofing material for the positive side waterproofing of basements, concrete slabs, in tanks, on flat roofs, underneath tiles, on terraces or balconies, and similar applications. Also suitable as a protective coating against mineral oils and aliphatic hydrocarbons. Bonds well to a wide variety of substrates including; masonry, concrete, screed, PVC, metal and bitumen.

General information

Uniclass 2015

Pr_35_31_68_47 Liquid tanking resinsPrimary


J30/10 Cold applied damp proofing

J30/110 Cold applied tanking . . . . . .

J30/130 Cold applied damp proofing . . . . . .

J31/10 Warm deck roof coating

J31/353 Waterproof coating

J31/5 Cold deck roof coating

Specification data - Liquid tanking resins

Product Reference

Köster 21

Standard product features


  • Colour: White.
  • Consistency: Paste.
  • Application temperature: 5–35°C.
  • Thickness per layer: 0.5–2.0 mm.

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