Delivering a Large-Scale Fire-Rated M-Tray® Green Roof in Crumlin, South Wales

In 2025, Wallbarn collaborated with Polyroof, Roberts Manufacturing, and Haran Roofing to deliver a large-scale modular green roof project in Crumlin, Caerphilly, South Wales. Covering over 1,200 square metres, the installation demonstrated how Wallbarn’s M-Tray® system can meet demanding technical, logistical, and fire safety requirements on complex roofing projects.

Meeting Fire Safety and Design Standards

The project was originally specified as a rollout green roof. However, concerns were raised by the architect regarding fire safety compliance. Wallbarn was able to confirm that the M-Tray® modular green roof system had undergone rigorous physical fire testing and is fully certified to B Roof(t4) standard, ensuring compliance with all relevant fire regulations.

This assurance provided the confidence to revise the specification in favour of M-Tray®, offering the client not only safety but also speed, flexibility, and long-term value.

Advantages of the Modular M-Tray® System

The decision to move from a rollout system to the modular M-Tray® brought several practical benefits. Each tray can be lifted individually for future maintenance, meaning the roof remains accessible without disturbing adjacent sections. This design also allowed for much faster installation, a key advantage given the project’s large scale and tight schedule.

Due to the roof’s pitch, Wallbarn recommended installing horizontal battens and structural parapets to prevent slumping or displacement of the green roof over time. The additional weight of a rollout system could have placed excess strain on the waterproofing membrane, but the modular nature of the M-Tray® trays eliminated that risk. These details were seamlessly integrated with Polyroof’s Protec liquid waterproofing system to maintain full membrane integrity.

Precision Logistics and Coordination

One of the most complex aspects of the project was logistics. The industrial estate location offered limited access, with no road closures or loading bays available. More than 5,000 M-Tray® modules were required, and delivery had to be carefully scheduled to align with installation progress.

Wallbarn organised a four-week delivery programme, transporting batches of 640 trays three times per week from its growing facility. Each delivery was managed in articulated lorry loads and coordinated to arrive just in time for installation. Nia from the Wallbarn Logistics Department maintained constant contact with Haran Roofing, Polyroof, and the transport team to ensure every stage ran smoothly and without delay.

A Collaborative Success

Thanks to precise coordination, expert planning, and teamwork across all parties, the project was completed on schedule and to full specification. The finished green roof provides not only a visually appealing and environmentally beneficial surface but also long-term durability, low maintenance, and strong fire performance credentials.

The Crumlin installation stands as an outstanding example of what can be achieved through effective collaboration and the intelligent use of modular technology. The project has since been nominated for multiple industry awards in both roofing and landscaping categories, recognising the quality, innovation, and technical excellence achieved by all involved.