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Siniat Weather Defence Board

Third party certifications:
  • BBA Agrément Certificate

    Certificate type


Glass fibre mat-faced, gypsum-based sheathing board.

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+44 (0)1275 377773 www.siniat.co.uk

A glass fibre mat-faced, gypsum-based board for use externally as a sheathing board. It is strong, highly moisture-resistant, non-combustible and has improved workability compared to traditional sheathing board products.

Manufactured to BS EN 15283‐1 types GM‐F, GM‐H1, GM‐I and CE marked.

Joints should be sealed with GTEC Fire Rated Silicone Sealant or GTEC Weather Defence Joint Tape.

Specification data
Product Reference

Siniat Weather Defence Board

Standard product features


Aerated calcium sulfate di-hydrate with liners constructed from polymers and glass fibre with moisture- and fire-resistant fillers/ fibres enclosed in gypsum core. Core and facers are bonded with starch. PVA edge glue. The board contains a water-resistant additive and a biocide to inhibit mould growth.


Purple on the front face and white on the back face.

Size (w x l):

1200 x 2400 mm.


12.5 mm.

Technical properties:

  • Weight: 10.8 kg/m².
  • Density: 860 kg/m³.
  • Thermal resistance (R-value): 0.05 m²K/W.
  • Thermal conductivity (to BS EN 12524): 0.25 W/m·K.
  • Water vapour resistance factor (to BS EN 12572): μ = 8.
  • Moisture content: <1%.
  • Moisture resistance: <3% (after two hours total immersion in water).
  • Longitudinal breaking load (to BS EN 15283‐1): ≥680 N.
  • Transverse breaking load (to BS EN 15283‐1): ≥310 N.
  • Reaction to fire: Non‐combustible, Euroclass A1 to BS EN 13501‐1, Class 0 to Building Regulations (E&W).

Third party certifications
  • 10/4725 : Product Sheet 4
  • 10/4725 : Product Sheet 5
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