Explore our brands

Have a question about our products or can't find what you're looking for ?

Contact Us
Back to product listing
High Performance Latex Underlayment

SX300 NA is a two part general purpose smoothing underlayment for interior applications.

SX300 NA is specifically designed for the preparation and smoothing of interior subfloors prior to the application of a liquid applied damp proof membrane and receiving a floor covering.

  • Water resistant: can be used for pre-smoothing
  • Excellent adhesion to a wide range of common flooring substrates, including:  concrete, sand/cement screeds, flooring grade asphalt, TREMCO surface DPM’s, etc.
  • Self priming on most surfaces
  • Short setting and cure time, facilitating fast track programs and minimising disruption
  • Low odour
  • Protein free


  • Ensure all surfaces to be coated are clean, dry, frost free and free from grease, oil, dirt, dust, loose friable material and any other contaminants (coating, laitance, etc).
  • Any surface hardener or curing compounds should be thoroughly removed prior to the application of SX300 NA. For full details of surface preparation contact tremco illbruck Technical Services.

In some case it may be necessary to prime with CS150 Acrylic Primer for porous substrates or CS100 Epoxy Primer for non-porous substrates. Always check with the tremco illbruck Technical Services.

Gradually add Part A to Part B, continually mixing with a slow speed drill and paddle.  Mix the contents for 2 - 3 minutes to obtain uniformity in colour and consistency.

SX300 NA should be applied directly after mixing by pouring a ribbon of material along the wet edge and then trowelled to form a smooth, even finish. The effective use of spike rolling can reduce visible trowel marks.

Protection on Completion
Ensure the screed is not subject to draughts during the first 6 hours of curing as this may lead to cracking and crazing. Tape up doorways with polythene to prevent air movement.
Prevent contamination by following trades (e.g. plastering), including water spillage.

Technical data

CompositionCementitious powder and liquid latex dispersion  
Pot Life
(at 20°C)
20 minutes
Compressive StrengthAfter 28 days approx. 21.9 N/mm²
Tensile Strength28 days 1.4 N/mm²

Thicknesses of 6 mm to feather edge can be applied dependant on surface profile. An average thickness of 3 mm will provide a coverage rate of 5 m² per mix

Thicknesses of 8 mm to 30 mm can be achieved by incorporating an equal volume of 3 mm granite chippings

This will depend on the condition of the substrate and method of preparation (please refer to tremco illbruck Technical Department)

Cure Time
(at 20°C)
Between 2 - 4 hours for foot traffic and 8 - 12 hours for application of damp proof membrane, floor covering and loading
StorageStore in dry, shaded conditions between +10°C and +35°C
Shelf Life6 months when stored as recommended in original unopened packaging
High temperatures and humidity will lead to a reduced shelf life

Product Finder

Application Area