5 Broadgate is a concrete decked, steel framed construction with a large, flat roof, virtually the size of a football pitch. ‘Hot melt’ roofing is often the go to solution for projects of this nature – whereby bitumen is heated to melting point and applied in two thin layers, with a reinforcement layer between. British Land has used hot melt on the majority of their buildings on the Broadgate estate to date, even as far back as the first buildings in 1984, so they have first-hand experience of its reliability and durability.
But it’s not a panacea – a hybrid solution with cold plastics was employed on several tricky details where the membrane was penetrated. And although hot melt is 50 per cent recyclable, it’s not the most sustainable solution on the market.
Creativity in roofing materials is still needed – even if it is purely for function rather than form – certainly if waterproof concrete or a cold plastic solution is advanced enough to bring down the cost and timescale factors, they’ll undoubtedly take the place of hot melt as the go-to-roofing-solution for buildings of this nature.