Smart Ballasting Solution for Fire-Rated Rooftop Decking

This rooftop redevelopment in central London required a fire-rated decking system suitable for use on an inverted warm roof. The project brief called for a solution that would provide the necessary ballast for the waterproofing system while delivering a sleek, low-maintenance finish for a high-traffic terrace. Working in collaboration with Fire Deck and ISW UK Ltd, Wallbarn supplied its fully Class A fire-rated substructure to support ExaDeck ceramic porcelain boards across the space.

To ensure inverted roof requirements, the build-up had to meet a minimum weight of 85kg per square metre. This was achieved by integrating 450 x 450 x 50 mm concrete slabs between the I-Plus aluminium joists. The bottom ledge of the joist allowed these slabs to be securely seated without making contact with the waterproofing insulation and without requiring mechanical fixings. This provided sufficient ballast while also mitigating the risk of wind uplift, a critical consideration given the building’s height and exposure.

Spreader plates were also used beneath each MetalPad Ex pedestal to distribute the load evenly and protect the insulation layer.

ExaDeck’s wood-effect porcelain boards deliver a warm, natural aesthetic alongside long-term durability. Their double-rectified construction ensures consistent dimensions and a perfectly flat base, allowing them to sit flush on Wallbarn’s aluminium joists. This contributes to their quiet, solid feel underfoot. The boards also offer excellent resistance to stains, scratches and slips, making them ideal for heavy foot traffic and public-facing terraces.

With a 25-year limited warranty and a projected lifespan of over 50 years, the system ensures long-term performance with minimal maintenance. This project demonstrates how modern Class A systems can achieve both technical compliance and architectural quality.