33 Central is one of the best-located office buildings in Central London, being located near London Bridge, Monument and Bank, as well as within walking distance of major cultural sites such as the Tower of London and Borough Market and London’s Cycle Superhighway. 

Sustainability was high on JRA (John Robertson Architects) list of requirements when designing the roof of the building. To aid biodiversity and slow rain water run-off, Radmat was contracted to supply the insulation, waterproofing and green roof materials. 

With a market leading guarantee the BBA certified, PermaQuik Hot Melt Monolithic Membrane waterproofing system is set to deliver exceptional performance providing weathertight protection for the ‘design life of the building’.

As the rooftop, designed by Townsend Landscape Architects comprised 40 species of plants and flowers, it was vital that this expansive landscape was completely watertight. The naturalistic planting includes large areas of perennial plant mixes interspersed by swathes of grasses covering earth mounds so it was important that the roots could not penetrate the waterproofing membrane and damage the roof.  Texsa Root Barrier P was used to ensure this was not compromised. Finshed with MedO Green Roof System to aid attenuation this completed the waterproofing system for this stunning rooftop garden in the heart of the City.

Radmat Building Products has supplied a comprehensive range of systems for the retrofitted Bracken House in the City of London, for The Financial Times, designed by JRA Architects for McClaren’s Construction. Radmat’s PermaQuik, ParaFlex and EshaFlex waterproofing systems with ProTherm Quantum PLUS⁺ and XPS Insulation have been installed during the refurbishment of the building, which includes a unique pizza-shaped roof design, offering spectacular views over the Capital, including St. Paul’s Cathedral and the Shard.

The Grade II listed refurbishment was not without its challenges for Partnering Contractors and Radmat. Situated in the City of London next to St Paul’s Cathedral, the team had to keep within a v3mm tolerance in order to meet the strict conservation height restrictions to preserve St Paul’s skyline.

Furthermore, the original warm roof was inaccessible, and so had to be stripped out. The works involved stripping the existing single ply and removing the insulation and VCL, before laying the Radmat PermaQuik Hot Melt Monolithic Membrane directly to substrate. Due to the proximity to St. Paul’s Cathedral, there was limited height available for insulation on this extensive refurbishment.  To meet the required 0.18W/m²K U-value within the existing 75mm insulation zone, ProTherm Quantum PLUS⁺ Hybrid was used with ProTherm Quantum PLUS⁺ Pure over the existing concrete plinths. This ensured the FFLs stayed within the conservation restrictions required. ProTherm XPS Infill was used to fill in the gaps and had to be hot wire cut so there was no stray insulation. The Quantum Insulation also had to be protected with ply wood so it wasn’t damaged or blown away. It was essential that the neigbouring buildings and the street level were protected.

The team also had to plan the logistics meticulously on this central London site, using hoists to transport materials to the roof.

An inverted hot melt system was used to create the multi-purpose roof garden, comprising break out areas, planters and a 150m roof-top running track. These had to be waterproofed to ensure no damage would leak through to the new roof. Radmat’s PermaQuik and EshaFlex systems were used with the peace of mind afforded by a ‘design-life of the building‚ guarantee to make sure this would not occur.

No concrete could be used on the running track due to fracturing, so the roof was constructed in a pizza shape to allow for the segmentation. FOAMGLAS^® was also used in these areas to ensure the roof had the compressive strength it needed.

The inverted roof required new water chutes and copper gutters (as the existing ones had become too fragile) to avoid pooling. These were protected with ParaFlex cold applied waterproofing membrane.