NBS Source
I'm a manufacturer

Koster SL Premium - Cement-based Levelling Underlayment

Verified by manufacturer 5 months ago

Delta Membrane Systems Ltd

Koster SL Premium - Cement based levelling, self-levelling underlayment or floor screed

Jump to:
+44 (0)1992 523523 Website


  • Suitable as a low-wear wearing layer in cellars or storage rooms.
  • Designed for leveling uneven concrete surfaces as well as for surfaces covered with KÖSTER VAP I 2000 vapor barriers.
  • It is intended for interior use.


Fast hardening cement based levelling, self-levelling underlayment or floor screed.

Features and benefits:

  • A high quality, fast setting underlayment that hardens tension free and provides a smooth, level surface ready to receive subsequent flooring systems.
  • It hardens within hours to a smooth, strong, and multifunctional levelling layer.
  • It may be applied onto a variety of substrates such as KÖSTER VAP I 2000 coatings, concrete, etc.
  • KÖSTER SL Premium accepts all major floor coverings and is compatible with most adhesives.
  • It is resistant to abrasion and wear.
  • If the material is installed onto smooth, non-absorbent substrates such as KÖSTER VAP I 2000 coatings, the substrate must be primed with KÖSTER VAP I 06 Primer.
  • It can be applied in layer thicknesses between 5 and 15 mm, can be feathered out to 2 mm, and installed in depressions up to 30 mm.
  • It cures quickly and crack-free with up to 90% reduced shrinkage.
  • Has a high surface hardness and a very good bond strength to the substrate.
  • KÖSTER SL Premium is not a decorative top coat, but is suitable as a low-wear wearing layer in cellars or storage rooms.
  • Consumption: Approx. 1.5 kg/m²/mm layer thickness.
  • Clean tools immediately after use with water.
  • Packaging (SL 280 025) 25 kg bag.


  • Store the material in a dry environment at temperatures between +10 °C and +30 °C.
  • In originally sealed packages, the material can be stored for a minimum of 6 months.


  • Wear protective gloves and goggles when processing the material.
  • Observe all governmental, state, and local safety regulations while processing the material.
  • Eye contact – Flush immediately with water and consult physician. Do not rub eyes. Skin contact – Wash off immediately with soap and water.

General information





Guidance for specification option:

Cement based levelling underlayment / screed.



Manufacturer guidance

25 kg

Warranty description

Ten year


Pr_35_31_06_80 Smoothing and levelling underlay compoundsPrimary


M10/19 Proprietary screeds to BS EN 13813

M10/160 Proprietary self smoothing levelling screeds

M50/460 Smoothing/ levelling underlayment compound

M40/460 Smoothing underlayment

M10/7 Proprietary quick drying levelling screeds

Specification data - Smoothing and levelling underlay compounds





Manufacturer guidance

  • The substrate has to be sound and solid as well as free of bond inhibiting agents such as grease and oil.
  • Remove all bond breaking substances such as laitance, loose particles, dust, formwork release oil, etc.
  • The substrate can be prepared according to need by shotblasting, grinding, or brushing.
  • Concrete and screed substrates are primed with KÖSTER SL Primer to reduce absorption before application.

Non-absorbent tile substrates must be removed or ground down to an absorbent layer.



Manufacturer guidance


  • The pull-off strength of substrates which are to be trafficked or that are to be treated with KÖSTER VAP I 2000 coatings must have a min. tensile strength of 1.5 N/mm².
  • Do not acid etch substrates or clean the substrate with chemicals.
  • Do not apply over adhesive residue. Do not bridge expansion joints with the KÖSTER SL Premium.
  • Expansion joints must be installed in accordance with local guidelines.
  • Mix each 25 kg bag of KÖSTER SL Premium with 5.2 l of potable water.
  • The water is placed in a clean mixing vessel and the powder added while constantly mixing.
  • Use an electrical paddle mixer and mix intensively for 3 minutes until a flowable, lump free consistency is reached.
  • Distribute the material in the desired layer thickness directly after mixing.
  • Mix and distribute the material in a constant work flow to avoid visible work edges.
  • The material is self levelling when working “fresh in fresh”.
  • While working larger areas use a KÖSTER Gauging Rake to distribute the material.
  • Rolling the surface with a KÖSTER Spiked Roller immediately after distribution creates a very smooth surface through better de-airing.
  • Install the KÖSTER SL Premium within 20 minutes.
  • Do not delay successive pours by more than 10 minutes to avoid visible work edges.
  • The surface qualities of the underlayment depend on workmanship, layer thickness, and curing parameters so that variations from a sample surface may occur.
  • Moisture sensitive floor coverings and sealers may not be applied before the material has fully cured.
  • Depending on the temperature it may take between 24 and 72 hours for the material to attain a residual moisture content of less than 3 M%.

Plain concrete without KÖSTER VAP I 2000 vapor barrier:

  • Concrete substrates are prepared by shot blasting, milling and/or sandblasting in order to achieve an absorbent, open pored substrate.
  • The cleaned concrete substrate is primed with KÖSTER SL Primer according to the Technical Guideline.

Concrete coated with a KOSTER VAP I 2000 vapor barrier:

  • When applying onto smooth, non-absorptive substrates such as KÖSTER VAP I 2000 systems, KÖSTER SL Premium can be applied in layers up to 12 mm.
  • It is necessary to prime such substrates with KÖSTER VAP I 06, consumption approximately 50 - 70 g/m².
  • Depressions in the substrate should be filled below the VAP I 2000 layer.
  • The coating can be opened to foot traffic after 24 hours and to traffic after 72 hours.

After treatment:

  • Curing can be aided by covering the hardened material with polyethylene sheets.
  • This reduces surface shrinkage tension especially when the material has been applied in thick layers.



Manufacturer guidance

  • Bulk density (powder): 1.3 g/cm³.
  • Compressive strength (28 days): approx. 45 N/mm².
  • Bending tensile strength (28 days): approx. 10 N/mm².
  • Tensile strength (depending on substrate): up to 4 N/mm²
  • Application temperature: min. + 5 °C to +30 °C.
  • Ideal application temperature: + 15 °C.
  • Pot life: 20 minutes (+ 20 °C).
  • Resistant to foot traffic after 3 – 4 hours*.
  • Can be tiled over after 4 – 6 hours*.
  • Trafficable (soft tires) after 24 hours*
  • Application of Parquet, carpet: after 24 – 72 hours*.
  • Application of synthetic flooring: after 24 – 72 hours.
  • Layer thickness (self-leveling), 5 to 15 mm in depressions up to 30 mm.
  • Not self-leveling: 2 to 5 mm.
  • Can be feathered out to 2 mm.

*depending on temperature.

Sustainability data

Contains Red List materials




Recycled content

As defined in clause 7.8 of BS EN ISO 14021

0 %


KÖSTER The Green Pages of Construction Chemicals

KÖSTER The Green Pages of Construction Chemicals

Similar products from Delta Membrane Systems Ltd

Koster SL Protect - High Wear Resistant Cement-based Underlayment

Koster SL Protect - High Wear Resistant Cement-based Underlayment