Flexible mortar adhesive ZK-U

  • for affixing wall, terazzo, milled rock tiles, etc.
  • for affixing large size tiles
  • on difficult and formable base surfaces
  • for horizontal and vertical surfaces
  • no vertical surface slip
  • very good adhesiveness to the base sur-face and to the tiles
  • very good working properties
  • frost- and water-resistant
  • for inside and outside use
Termo Organika® ZK-U adhesive is used for affixing wall, terrazzo, rock (except for marble), cement (including large size) and milled rock tiles to stable, non-formable mineral base surfaces, e.g.: reinforced concrete prefabricates, concrete (at least 6 months’ old), cement screeds (at least 28 days’ old), ceramic, Lightweight Expanded Clay Aggregate (LECA), and aerated concrete elements, natural stone, strong cement, lime and cement/lime plasters (at least 28 days’ old), etc., and on “difficult” and formable base surfaces, e.g. plasterboards, wood-like boards, in underfloor heating systems, painted surfaces, etc. It may be applied inside (in rooms used as dry, but also wet ones and exposed to damp) and outside (verandas, balconies, stairs, etc.).

Technical Data

Product conforming with EN12004: C2TEs1: Cement adhesive with enhanced parameters, reduced slip, extended curing time, formable.
Reaction to fire: (layer of 2÷6 mm)Class A2/A2fl
Initial adhesiveness:≥ 1,0 N/mm2
Adhesiveness after immersing in water:≥ 1,0 N/mm2
Adhesiveness after thermal ageing:≥ 1,0 N/mm2
Adhesiveness after freezing and defrosting cycles:≥ 1,0 N/mm2
Curing time: adhesiveness after no less than 30 minutes:≥ 0,5 N/mm2
Transverse deformation:≥ 2,5 N/mm2
Slip:≤ 0,5 mm
Estimated consumption of dry mix: *) 
Tile side length up to 10 cm Approx. 2,3-2,9 kg/m2
Tile side length up to 15 cm Approx. 3,4-4,3 kg/m2
Tile side length up to 25 cm Approx. 4,5-5,8 kg/m2
Tile side length up to 30 cm Approx. 5,6-7,2 kg/m2
Quantity of water:as per packaging
Initial curing time:approx. 10 minutes
To be used:within up to 4 hours
Hardening time: 
for pedestrian traffic: 2 days
full load: 14 days
walls: after 2 days
floors: after 4 days
Temperature of application and of the base surface:+5°C ÷ +30°C
Storage: 12 months from date of manufacture, in origi-nal, sealed bags, stored on palettes.

*)Assuming that the tiles are covered with the mortar in 70%-90% and affixed on a smooth surface.

 Preparation of the Surface

Every base surface must be compact, smooth, load-bearing, dry, clean and without any film (grease, dust, remnants of paint, etc.) which would reduce adhesiveness. Remove old “loose” plaster, peeling paints and other dirt. Minor uneven spots and cavities may be repaired with ZK-U adhesive. Smoothen, level out or provide the floors with the appropriate gradients. Waterproofing with the appropriate preparations is recommended for rooms potentially exposed to damp in future. Complete the base surface repairs at least 1 day before affixing the tiles. Absorbent surfaces (e.g. aerated concrete) should be treated with TO-GU universal primer, and smooth and/or non-absorbent surfaces (e.g. con-crete, reinforced concrete) with TO-GS contact primer.


Pour the bag content into a vessel with the recommended minimum quantity of water and mix with a low-speed electrical mixer until smooth paste-like consistency is achieved. Put aside the adhesive for approx. 10 minutes, mix again gently and check the consistency. The consistency of the material can be adjusted by adding water, but in a quantity which does not exceed the upper limit. Prepare portions of the mortar which will be used within approx. 4 hours. Stir the mortar which has thickened in the meantime without adding water. Do not soak the tiles in water. Choose the size of the teeth of the tooth trowel to match the tile size. Apply ZK-U adhesive on a small surface with a smooth trowel. After application, spread evenly with a tooth trowel. Affix dry and clean tiles immediately (before a matt “skin” appears on the surface of the mortar), pressing them firmly, and then adjust to the right position. Correctly affixed wall tiles should be covered with the mortar on at least 70 – 90%, and floor tiles on 100% of their surface. Application of an additional thin layer of ZK-U mortar on the back of the affixed tiles will help attain a 100% coverage of the tile with the adhe-sive. Especially tiles affixed on areas exposed to damp and frost and on difficult base surfaces must be covered with the adhesive in 100% (this applies to tiles placed on both horizontal and vertical surfaces). In order to affix large size tiles (of more than 20 cm x 20 cm) on horizontal surfaces, the mortar may be mixed with slightly more water to get less thick consistency of the adhesive. The position of a freshly affixed tile may be ad-justed during another 10 minutes approximately (depending on the temperature and humidity). Tiles on walls may be applied from any point with-out the need to apply baseboards. Do not place the tiles in a butt arrangement but leave joints whose width depends on your individual prefer-ences and needs (usually 2-8 mm). Appropriate distance crosses help to produce joints of the same width. Remove excess mortar from the joints. Make expansion joints at points of dilatation, cracks, joints of prefabricates, shrinkage joints, etc. Fill in the dilatations and internal connections between the walls and the floor will flexible fillers or special expansion profiles. The temperature of the environment, of the base surface and of the affixed tiles during the work and during at least the next 24 hours should be above +5°C. Do not use rusted or dirty tools. Rinse off fresh smudges with water. After it hardens, the mortar can only be removed mechanically. The adhesive may not be mixed with cement, lime, sand, other adhesives, mortars and chemical additives. Do not add more water than the specified range.


The product contains cement and, after mixing with water, it creates an alkaline reaction. Do not inhale the dusts and avoid being splashed with the mortar. In case of contact of the product with eyes or skin, rinse them with plenty of water and seek medical advice, wash the skin with water and soap. Keep away from children. During work, wear protective clothing and eye protectors

 User safety

In addition to the above recommendations, follow good building practice and work-safety rules. The manufacturer warrants the quality of the product but has no influence on the manner, place and conditions of its storage and application. Building work should be done by professionally qualified contractors.

Technical sheet Flexible mortar adhesive ZK-U(0.33MB)pdf  download


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