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Calcium sulfate based screed for use above ten storeys. It is a blend of Gyvlon binder, special additives and selected aggregates mixed with clean potable water to produce a pumpable, self smoothing, flowing screed (manufactured to BS EN 13813).

Specially formulated to help reduce moisture loss to pump lines and in line segregation whilst maintaining all the normal features of a Gyvlon flowing screed. Specialist pumps may be required over certain heights.


  • Easily achieves SR2 finish as described in BS 8204.
  • Excellent thermal conductivity.
  • Ideal for use with under floor heating and gives excellent performance compared to floating floors.
  • Increased productivity - up to 1200 m²/day can be achieved.
  • Minimal thermal expansion (0.012 mm/mK).
  • No need for loading out prior to flooring.
  • Protein free - cannot harbour harmful bacteria.
  • Self compacting.
  • Self curing.


Requires priming prior to application of adhesives; generally acrylic dispersion or water based epoxy.

Standard product features


Off-white fluid mortar.


  • Dry: 2000 kg/m³.
  • Wet: 2200 kg/m³.

Technical properties:

  • Compressive strength class (BS EN 13813): C25.
  • Flexural strength class (BS EN 13813): F4.
  • pH: >10.


Sub base:

Gyvlon screeds are suitable for application to most types of sub bases, demonstrating an excellent degree of dimensional stability (maximum shrinkage/ expansion on drying of 0.02%) when compared to traditional sand/ cement based screeds.

Application thickness (minimum):

  • Bonded: 25 mm.
  • In contact with substrate: 30 mm.
  • Unbonded: 30 mm.
  • Floating commercial: 40 mm.
  • Floating domestic: 35 mm.
  • Underfloor heating: 25 mm (30 mm nominal) cover to pipes, heating elements.

Drying time:

  • Dries at a rate of 1 mm per day up to a screed depth of 40 mm in good drying conditions.
  • Can be walked on in 24-48 hours.
  • Can be loaded after 7 days.
  • Can be force dried as early as 7 days after application.

NBS Specification

NBS Create logo
This product is associated with the following NBS Create clause:
45-55-10/310 Proprietary levelling or wearing screed to BS EN 13813

NBS Specification

NBS Buliding logo
This product is associated with the following NBS clauses:

Product specification

An important note about specifying



Anhydritec Ltd


+44 (0)1925 428780

Product reference

Gyvlon Sky


 - Minimum:
[ ______ ]
 - Nominal:
[ ______ ]

Manufacturer details

221 Europa Boulevard,
Cheshire, WA5 7TN
Tel +44 (0)1925 428780
Fax +44 (0)1925 428788
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