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Bostik Cempolay Ultra Strong Self Levelling and Resurfacing Compound 25Kg – Pallet Deals and Bulk Buy

Bostik Adhesives and Levellers - Terrific Pallet Deals and Bulk Buy

Bostik Cempolay Ultra Strong Self Levelling and Resurfacing Compound

A strong, fast setting resurfacing & smoothing compound

Bostik Cempolay Ultra Strong is a fast setting smoothing compound that can be applied up to 20mm thick.

Water and frost resistant, this compound can be used to smooth and level sub floors prior to laying decorative floor coverings.

It is also suitable for use in an external garage as an underlay and can withstand foot traffic in just 2 hours.

  • Rapid setting
  • Smooths and levels up to 20mm thick
  • Suitable for exterior use as an underlay and internally can be left as a final wear surface which can be over painted
  • Water and frost resistant once cured
  • Suitable for use with underfloor heating
  • For interior and exterior use

Bostik Cempolay Ultra Strong Self Levelling and Resurfacing Compound extended information


Approx. 7.3m2 per bag at 2mm depth
Approx. 5m2 per bag at 3mm depth
Approx. 3m2 per bag at 5mm depth
Approx. 0.75m2 per bag at 20mm depth

(depending on the smoothness of the floor surface & application technique)

Bostik Cempolay Ultra Strong is strong, fast setting, protein-free, resurfacing & smoothing compound for levelling interior subfloors prior to laying decorative floor coverings, or painting. It is also suitable for some exterior applications, prior to laying ceramic tiles, slabs & natural stone, and can also be used on domestic garage floors prior to over coating with a suitable floor paint.

It is ideal for smoothing and levelling prepared concrete subfloors, sand/cement screeds and unglazed ceramic tiles.

It can be extended for filling holes and forming sloping screeds (5% downward gradients).

It is suitable for use with warm water underfloor heating systems, provided a surface temperature of +27°C is not exceeded. It is not suitable for use on tarmac, vinyl, or floors prone to structural movement.

All phases of installation should comply with the latest editions of:

BS 8102 Code of Practice for protection of structures against water from the ground.

BS 5325 Code of Practice for installation of textile floor coverings.

BS 8203 Code of Practice for installation of resilient floor coverings.

BS 8201 Code of Practice for installations of for flooring of timber, timber products and wood based panel products.

Bostik Cempolay Ultra Strong Product Characteristics

FormDry, free-flowing powder
Specific Gravity1.6 approx
CompositionBlend of cement and fillers
Product Codes0812526 25kg bag
Storage/Shelf LifeStore and transport securely. Store for up to 6 months from date of manufacture in original, unopened packaging, clear of the ground, in cool, dry conditions within the temperature range +5°C to +25°C and out of direct sunlight. Protect from excessive drafts, frost, damp, condensation and dew.

Bostik Cempolay Ultra Strong typical performances

+5°C to +25°C
CoverageApprox. 7.3m2 per bag at 2mm depth

Approx. 5m2 per bag at 3mm depth

Approx. 3m2 per bag at 5mm depth

Approx. 0.75m2 per bag at 20mm depth
(depending on the smoothness of the
floor surface & application technique)
Gauging LiquidWater
2mm to 20mm
Working Times15 to 20 minutes after mixing (depending on ambient temperatures)
Drying TimesFoot traffic: approx. 2 to 3 hours at +20°C

Ceramic tiles: approx. 3 hours at +20°C

Impervious floor coverings: approx.
24 hours per 10mm depth at +20°C
CleaningClean tools and equipment with
warm, soapy water immediately after


1. Ensure the subfloor is sound, clean, dry and of adequate tensile and compressive strength, free from loose material, laitance, cracks and structural defects. Ensure there is an effective damp-proof membrane, which conforms to BS 8203.

2. The subfloor should be tested in accordance with British Standards, using a properly calibrated and insulated hygrometer. A reading of 75% RH or less confirms that the subfloor is satisfactorily dry.

3. Any contaminants that may hinder adhesion, such as grease, oil, dirt, dust, plaster, some curing compounds, surface hardeners, additives and adhesive residues must be completely removed. Bostik Cempolay Ultra Strong does not tolerate any contamination.

4. Any cracks or holes in the floor must be cleaned out and filled with Bostik Rapid Repair Mortar. Allow to dry before applying Bostik Cempolay Ultra Strong.

5. For optimum performance, a room temperature of +13°C to +18°C should be maintained for at least 24 hours prior to application. The temperature of the subfloor must be at least +5°C throughout the application and drying of the smoothing compound. Ensure that a maximum room temperature of +25°C is not exceeded during application. Do not apply externally if temperatures are likely to drop below freezing within 7 days of application. The temperature must remain above +5°C.

Underfloor heating systems:

6. Warm water underfloor heating systems must be switched off for 48 hours before installation. Wait 48 hours after installation before gradually turning up underfloor heating.


7. Prime porous surfaces with Bostik SBR diluted with 4 parts water. Allow to dry before applying Bostik Cempolay Ultra Strong.

8. Prime non-porous surfaces/unglazed ceramic tiles with undiluted Bostik SBR, and apply Bostik Cempolay Ultra Strong while it is still tacky, usually about 30 minutes. If it has dried, apply a further coat of Bostik SBR.


Smoothing compound:
– 5 litres of water to 25kg Bostik Cempolay Ultra Strong.

Bulked out compound:
– 4 litres of water to 25kg Bostik Cempolay Ultra Strong + 12.5kg of dry, sharp sand (0mm to 4mm).

– Or, 4 litres of water to 25kg Bostik Cempolay Ultra Strong + 12.5kg of granite chippings (3mm).


9. According to the mix ratios above, pour clean, cold water into a clean mixing bucket. Gradually add Bostik Cempolay Ultra Strong powder to the water, whilst continually mixing with an electric drill and mixing paddle until a smooth, lump-free mixture is obtained.

10. Do not mix more compound than you can use in 15 to 20 minutes. The mixture will remain workable for approximately 20 minutes under normal conditions. If the mix begins to stiffen before it has been spread, it must be discarded. Do not re-temper, or add further water. Note: the addition of too much water may result in separation of the compound.

11. It can be applied from a minimum depth of 2mm, up to 20mm in a single application. However, when applying at depths greater than 10mm it may be beneficial to bulk out the compound with dry, sharp sand or granite chippings.

Bulked out compound:
12. The sand or chippings must be dry and added after mixing the water and powder together. Use the mix ratios and mixing process detailed above.

NOTE: Bulked out compound is not suitable for use with underfloor heating systems.


13. Pour the mixed material onto the prepared subfloor in a continuous operation and allow to flow.

14. Using a steel screeding trowel, spread evenly to the required depth and smoothness.

15. Protect surface from foot traffic prior to laying a floor covering. Ensure the compound is fully dry before applying a floor covering.


16. Protect freshly applied product from strong sunlight and through draughts, as this can dehydrate the product, resulting in incorrect curing. Also, protect from rain and frost. Do not force dry the smoothing compound, as this may affect the curing process.

17. Application in high temperatures may result in rapid setting and poor flow. The rapid loss of water may increase the risk of cracking.

18. The drying time depends on how absorbent the subfloor is, the air humidity and both the ambient & floor temperatures.

19. Under good site conditions, it will normally take foot traffic 2 to 3 hours after application. Leave overnight before applying impervious floor coverings, or 24 hours for every 10mm. Ceramic tiles may be laid in as little as 3 hours, when a cement-based adhesive is used. The walk on time and setting time will be delayed if the powder has been stored in temperatures below +10°C, or has been
applied in temperatures below +20°C.

20. The working and drying times of the compound will be reduced in higher temperatures and increased in lower temperatures.


21. If Bostik Cempolay Ultra Strong is to be left exposed as a wearing surface on domestic garage floors, apply a suitable transparent varnish or paint to protect the compound. Externally, it must be covered by ceramic tiles, slabs or natural stone.


22. Clean tools and equipment with warm, soapy water immediately after use. Remove surplus compound from surfaces whilst it is still wet. Cured material can only be removed mechanically.

Bostik Cempolay Ultra Strong PRECAUTIONS IN USE

Do not use as a substitute for a DPM. An effective membrane is required to prevent water entering the system.

The mix ratios and temperatures need to be followed accurately. Changing the mix ratios will disrupt the system and risk product failure.


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