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Sarnafil G476-SA Ballasted Inverted Roof System

Sarnafil G476-SA Ballasted Inverted Roof System

Third party certifications:
  • BBA Agrément Certificate

    BBA Agrément Certificate

    Certificate type

Sika Sarnafil

Self-adhesive PVC-P single-ply system using a membrane with foam backing, for inverted ballasted applications.

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+44 (0)1707 394444 www.sarnafil.co.uk

Self-adhesive PVC-P single-ply system and a foam backing coated with a pressure-sensitive adhesive, for inverted ballasted and green roof systems.

System includes:

  • Paving, stone ballast or green/ brown roofs (supplied by others).
  • S-Felt VS 140 filter layer.
  • SarnaTherm XPS insulation.
  • Sarnafil G476-SA waterproof membrane.

- Filter layer:

A 140 g/m² polypropylene based fleece, grey in colour, suitable for use as an inverted roof filter layer in loose laid ballasted systems. Sarnafil Type VS is UV stabilised and can be left exposed to weather.

- Insulation:

Unfaced extruded polystyrene CFC and HCFC free thermoset cellular plastic insulant, with a rigid closed cell structure. SarnaTherm XPS is manufactured to BS EN 13164 'Thermal Insulation products for buildings - factory made extruded polystyrene foam (XPS)'.

- Waterproof membrane:

Sarnafil G membranes are manufactured using a state of the art extrusion coating process that eliminates shrinkage and plastic memory and produces a dynamically stable membrane.


Certified by BBA, in their opinion, to have a "life expectancy in excess of 40 years" for exposed applications, with periodic maintenance as stated below.

"A planned maintenance cycle, including inspections by the Certificate holder at minimum intervals of five years, should be introduced if an extended service life is required. The Certificate holder can advise on methods of extending the service life. This could include the use of thicker membranes, specific maintenance requirements or localised replacement and repair."

Should the maintenance cycle not be followed Sarnafil G/S membranes have been given, by the BBA in their opinion, a life expectancy of "in excess of 35 years".


- Filter layer:

Sarnafil Type VS is loose laid, with 300 mm side and end laps.

- Insulation:

The insulation is to be laid loose, with boards lightly butt jointed and level. The specified ballast should be installed as soon as possible, once the filter layer is laid. Until the ballast is laid, the loose laid insulation will be vulnerable to wind uplift forces. If it is necessary to delay ballasting the roof, then temporary ballast, such as bagged gravel or sand, should be strategically placed across the completed roof areas.

Project specific fixing details must be ascertained from the latest Sarnafil project specification.

- Waterproof membrane:

Sarnafil G476-SA is self-adhered directly to approved substrates primed with Sarnafil Primer 600 or Spray Primer 610. Side laps are heat welded using the 80 mm wide salvage edge, end joints are butted together and weathered using Sarnafil G410-EL membrane.

Installation is carried out by Sarnafil trained contractors.

General information

Uniclass 2015

Ss_30_40_30_79 Single layer sheet inverted roof covering systemsPrimary


J42/120 Inverted roof covering

Specification data - Single layer sheet inverted roof covering systems

Product Reference

Sarnafil G476-SA Ballasted Inverted Roof System


Not required

Primer 110

Primer 600

Spray Primer 610




SarnaTherm XPS


Loose laid

Waterproof membrane



Sarnafil G476-SA


Signal Red




Double L rainwater outlets

G/S rainwater outlets

Sarnafil Constant Force post

Sarnafil heat weldable lightning conductor clips


Sarnaplast 2235

Standard product features

Filter layer:

  • Thickness: 0.5 mm.
  • Roll width: 2.0 m.
  • Roll length: 50 m.


  • Thermal conductivity: 0.029W/m²K (thicknesses < 120 mm).
  • 0.031W/m²K (thicknesses > 120 mm).
  • CFC/ HCFC free.
  • Zero ODP (Ozone Depletion Potential).
  • Typical Density of 33 kg/m³.
  • Compressive strength 300-500 kPa at 10% deformation.
  • Withstands freeze/ thaw cycling.
  • Closed cell structure minimises water absorption.

Waterproof membrane:

- Thickness:

3.0 mm overall thickness.

- Width

2.0 m.

- Length of roll:

20 m.

- Weight:

2.20 kg/m².

Product Options


- Thickness:

Consult Sika Sarnafil for recommendations and details.


  • Double L rainwater outlets: Insulated outlets.
  • G/S rainwater outlets: Injection moulded PVC outlets and scuppers.
  • Primer 110: Surface primer creating a key for Sarnaplast 2235.
  • Sarnafil Constant Force post: Cable-based fall arrest and restraint system.
  • Sarnafil Double L: High drainage capacity insulated rainwater outlet.
  • Sarnafil heat weldable lightning conductor clips.
  • Sarnametal: Galvanized metal sheet with Sarnafil G410-12EL factory laminated to it, for use in prefabricated flashings and drip details.
  • Sarnaplast 2235: Elastic one-part silicone sealant for sealing edges and perimeter upstand flashing terminations.
  • Sarnafil Primer 600
  • Sarnafil Spray Primer 610.

Third party certifications
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