Description
SikaLastic-1K is a one-component, crack-bridging, fibre-reinforced cement mortar modified with alkali-resistant polymers, built for flexible waterproofing of concrete tanks, basins and pipes, and for wet-area waterproofing under tiles in bathrooms, showers, terraces and balconies. Being one-component means only water needs to be added on site — no separate liquid polymer component to measure and mix in, which simplifies quality control on a job compared with a two-part system.
Its crack-bridging ability and good sag resistance mean it can be applied confidently on vertical surfaces without excessive tooling, and it can be applied directly to damp substrates, which matters on real renovation or below-grade jobs where a fully dry substrate isn’t always achievable. For negative water pressure applications — basement walls and floors being pushed by groundwater from the outside — it’s specifically recommended, provided the correct layer thickness and cure time are respected.
Technical Specifications
| Composition | Cement modified with alkali-resistant polymers, fibres, aggregates |
|---|---|
| Appearance / colour | Light grey powder |
| Mixing ratio (brush) | ~6.0L water per 20kg bag |
| Mixing ratio (trowel) | ~4.4L water per 20kg bag |
| Consumption | ~1.2 kg/m²/mm |
| Layer thickness (standard) | 2mm DFT, minimum 2 layers |
| Layer thickness (negative pressure/immersed) | 3-4mm DFT, minimum 2 layers |
| Pot life | ~30 minutes at +20°C |
| Ambient/substrate temperature | 5°C min. / 35°C max. |
| Packaging | 20kg bags |
Where to Use
- Flexible waterproofing of concrete tanks, basins and pipes
- Bathrooms, showers, terraces, balconies and swimming pools before tiling
- External wall surfaces to be backfilled in ground
- Inside waterproofing against negative water pressure in basement walls and floors
How to Apply
- Mix — add the powder to water at the correct ratio for brush (~6.0L/bag) or trowel (~4.4L/bag) application.
- Apply the first layer — by brush, spray or trowel, up to 1mm (brush) or 2mm (trowel) per layer.
- Apply the second layer — build up to the required total DFT (2mm standard, 3-4mm for negative pressure or immersed use).
- Do not float or trowel smooth — the surface should not be smoothed with a float or trowel.
- Allow to cure fully — before overcoating, tiling or water contact, respecting the temperature-dependent waiting times.
Important Notes
- Protect from rain for at least 24-48 hours after application.
- Avoid direct contact with chlorinated water (e.g. swimming pools) unless suitably protected.
- Contact with drinking water requires full hardening and compliance with local drinking-water regulations — allow the longer waiting time (~15 days).
- Shelf life is 6 months from production, stored cool and dry, protected from water.
