Void Form System

Permanent Void Formwork | GRP Grating | Fall Protection

Permanent Void Formwork

At Stair Formwork Ltd, we have engineered a smarter, safer solution for creating voids in concrete cores. Our Void form system combines hot-dipped galvanised steel boxes with high-performance GRP (Glass Reinforced Plastic) structural grating to deliver permanent formwork that eliminates the need for traditional striking and reduces on-site risks.

Stair Formwork

Permanent Formwork, Permanent Safety

Traditional void formation often requires temporary supports and introduces significant safety hazards. Our system is installed before the slab pour, immediately creating a secure, permanent opening. This proactive approach dramatically reduces the risk of falls from the leading edge during the construction phase, addressing one of the most critical Health and Safety challenges on site.

Once the concrete is poured, the formwork remains in place—there is no “striking” required. This ensures perfect dimensional accuracy for the void every time.

Stair Formwork

GRP Grating: Lightweight, Strong & Fire Compliant

The surface of our void forms utilizes GRP protruded fiberglass structural profiles with molded anti-slip grating. Manufactured as standard in RAL 6017 (Green) , this grating is specifically chosen for M&E riser projects due to its excellent performance characteristics:

  • Fire Performance: Our GRP is produced to Class B BS EN13501, superseding older BS 476 standards. It has been tested to BS476 for Class 1 Spread of Flame and Part 6 heat release, ensuring compliance with the strictest commercial fire regulations.
  • Strength and Open Area: The 38mm GRP mesh has been subjected to rigorous deflection testing, proving its capacity to withstand substantial UDL loads across various spans. With an impressive 70% open area, it is ideal for ventilation and service access while maintaining structural integrity.
  • Non-Corrosive: The GRP components are impervious to corrosion, ensuring long-term durability in internal environments.
Stair Formwork

Fire Resistance

The galvanised steel components of the void form share the same robust fire performance as our stair systems.

The steel is zero-rated, with a melting point exceeding 1370°C, and has successfully passed 2-hour radiant heat testing, ensuring the void maintains its integrity in the event of a fire.

    Stair Formwork

    Installation & Protection

    The system is designed for rapid installation. Galvanised steel boxes are fixed in place using M12 fixings, with M-Clips provided for secure GRP grating attachment.

    We also supply black Correx sheeting to protect the void during follow-on trades.

      SHORT LEAD TIMES. HIGH QUALITY DRAWINGS.

      For technical drawings, load calculations, or to discuss a bespoke project, contact our design team in Huntingdon today.

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