Sikalastic-1K GB – Flexible Waterproof Mortar 20kg

Sikalastic-1K GB is a one-component, fibre-reinforced cementitious waterproofing mortar used for flexible waterproofing and concrete protection. It is designed for concrete structures that may be exposed to slight movement, moisture ingress or demanding service conditions. Typical uses include tanks, basins and pipes, bathrooms and showers, terraces and balconies, swimming pools before tiling, basement walls and floors, and external walls that will be backfilled into the ground. It can also be used as a protective coating on reinforced concrete to help improve durability against freeze-thaw conditions and reactions to carbon dioxide.

The water dosage depends on the application method. For brush application, use around 6.0 litres of water per 20kg bag. For trowel application, use around 4.4 litres of water per 20kg bag. The product should be mixed with a low-speed drill and paddle until it becomes fully homogeneous and lump free, then mixed for a further 3 to 4 minutes. No extra water or other ingredients should be added, and each full bag should be mixed in one go.

Sikalastic-1K GB can be applied by brush, trowel or suitable spray equipment. For the best waterproofing performance, it should be applied by trowel in at least 2 layers to a total thickness of at least 3mm. When applying by brush, each layer should be no more than 1mm thick and the product should be built up in 2 to 3 coats, with each coat applied crosswise to help achieve even coverage. The first layer must be dry before the next coat is applied. The finished application should cover the whole surface evenly, and the product should not be smoothed with a float or sponge trowel. Once fully cured, the surface can be lightly abraded if a smoother finish is needed.

The substrate should be sound, clean and free from anything that could reduce adhesion, such as dust, grease, oil, laitance, old coatings or surface treatments. Concrete repairs should be completed before waterproofing begins, and the substrate should be dampened ahead of application. It should not, however, be wet to the touch. Junctions around pipes, fittings and changes of direction should be properly sealed, and floor-to-wall junctions should be formed with coved details to help maintain a watertight system.

Sikalastic-1K GB must be fully hardened before it is tiled over, coated or brought into contact with water. At around 20°C, horizontal tiling, water-based coatings and water immersion are typically possible after about 2 days. At lower temperatures, these waiting times can be longer. For contact with drinking water, the waiting time is around 15 days. Actual drying and hardening times will vary depending on temperature, humidity and site conditions.

Yes. Sikalastic-1K GB should be applied when air and substrate temperatures are between 5°C and 35°C. It should be protected from rain for at least 24 to 48 hours after application, and it should not be applied in direct sun, strong winds or when rain is imminent. In enclosed areas such as basements, higher humidity can slow the set, so good ventilation is recommended. The product is vapour permeable rather than a vapour barrier, and if it is to be overcoated with a solvent-based paint, a compatibility test should be carried out first. Tools should be cleaned with water before the product sets, as hardened material can only be removed mechanically.