Class A Rated Substructures for Paving or Decking

Wallbarn

The Wallbarn fire-rated substructure system for Paving or Decking

Wallbarn’s Class A Substructure System is designed specifically for fire-rated decking and paving applications on projects where non-combustible materials are mandatory. Every component within the system is Class A rated to EN 13501-1 and compliant with Approved Document B, BS 8579 and related regulations governing external wall and balcony construction.

Under current legislation, the external envelope of a building above 11 metres must be constructed using non-combustible materials. This requirement applies directly to balconies, terraces and podium decks. Wallbarn’s Class A system provides a complete, fully metal substructure solution including all rails, joists, pedestals, connectors, fixings and accessories to ensure full compliance on fire rated schemes.

System Components & Options

A complete aluminium joist and MetalPad Ex pedestal assembly for non-combustible paving and decking systems. Rails are connected via wing nut and bolt fixing for rapid, adjustable installation. Fully compliant and ideal for new build & retrofit projects with fire safety requirements.

MetalPad Ex Pedestals
100 percent metal Class A adjustable pedestals supporting the full range of aluminium rails and joists. The range covers heights from 26mm to 375mm and have a Zintec 200 coating for external durability. Provides a stable, load-bearing platform for decks and paving.

Joist Hanger
A Class A rated fixing designed for refurbishment and retrofit projects where the substructure must be installed onto an existing steel frame, I-beams or where a traditional subfloor is absent. The Joist Hanger provides a secure mechanical connection between Wallbarn aluminium rails and the supporting structure, ensuring stability, alignment and continuity across the deck. It allows installers to create a compliant, non-combustible substructure even in challenging conditions where standard pedestal placement is not possible.

Aluminium Box Rails
6063 T6 extruded aluminium rails available in 15mm, 20mm and 25mm heights. Originally developed as an ultra-low alternative to timber, now widely used due to strength, weight and ease of installation. Connects directly to MetalPad Ex and Ultra Low Joist Holders.

Aluminium I-Plus Rails
High-strength 50mm, 75mm and 100mm aluminium joists designed for larger spans and greater height thresholds. Connects to MetalPad Ex for an integrated and extremely durable substructure. Suitable for paving or decking schemes.

Ultra-Low Joist Holder
Designed for projects with very restricted build-up. Achieves a Class A rated substructure from as little as 17mm while remaining compatible with all Wallbarn aluminium rails. Particularly ideal for refurbishment and retrofits where low height systems are required.

Rail to Rail Headpiece
Enables rail-to-rail stacking to achieve greater height thresholds and complex build-ups. Maintains structural rigidity across larger decks.

Connectors, Fixings and Brackets
Straight and right-angle fixing brackets, wing nut kits, self-tapping screws and rail connectors and brackets create a complete mechanical substructure solution with zero plastic or rubber components.

Paving Headpiece
Class A rated headpiece designed to support porcelain or concrete paving slabs. It fits directly onto Wallbarn aluminium Box Rails, I-Plus Beams or the MetalPad Ex adjustable pedestal, providing accurate tile positioning and consistent joint spacing between tiles or slabs for drainage.

Spreader Plate
For use beneath MetalPad Ex pedestals & Ultra-Low Jooist Holders to improve weight distribution on vulnerable subfloors such as roofing membranes or insulation.

Key Advantages
• Fully Class A rated system, compliant with EN 13501-1, BS 8579 and Approved Document B
• Complete metal substructure with no combustible elements
• Extensive height options from 17mm to over 1 metre
• Suitable for both paving and decking applications
• Lightweight, strong extruded aluminium components reducing loading
• Large pedestal spacing reducing the number of supports required
• Adjustable, precise installation using flexible components and accessories
• Multiple build-ups available to solve challenging thresholds and complex detailing
• Designed for long-term performance with no rotting, warping or corrosion
• Greater flexibility with installation as the frame can be connected loosely using the wing nuts, finely adjusted and then the nuts tightened once exact levels have been confirmed

Technical Support
Wallbarn’s Technical Team provides extensive guidance throughout the lifecycle of a project, supporting specifiers and contractors with drawings, take-offs, layouts and compliance advice. From concept to design to delivery and beyond, our specialists ensure your Class A decking or paving system is fully compliant and built for long-term performance.