SOLUTIONS FOR A GREEN ROOF RENAISSANCE

A well-planned flat roofing system can serve as a functional surface, adding entire new useable areas to a building, as well as increasing its versatility. Especially the importance of accessible green spaces in the urban landscape has grown over the years – as has the lobby for green roofs. At SOPREMA, we offer a green roofing service that creates the eco-friendly surfacing solution our buildings need to be future-proof. In what follows, we discuss important specification considerations for green roof build-ups. A GREENER CITYSCAPE The current biophilic transformation, which is taking place not only in for instance San Francisco (which requires every new building to have a green roof) but all over the UK as well, is only sustainable if the whole roof build-up is considered early in the specification process. The increased loading and drainage requirements of a green roof build-up mean that a resilient, durable and long-lasting structural waterproofing system is essential. Our cities will not become urban oases overnight but selecting the right roof build-up will enable specifiers to maximise the opportunity to feed our appetite for green spaces. HOT MELT FOR GREEN ROOFS Although cold-applied liquid membranes and single ply roof coverings are sometimes used as part of a green roof build-up, hot melt structural waterproofing systems are by far the most frequently-specified choice for green roofs. The main reason for this is that they offer a robust and versatile solution that bonds to the roof substrate to form a homogenous surface, with a service life comparable to the expected life of the building. Once the system is fully bonded to the roof surface, water cannot track beneath the waterproofed layer, ensuring complete protection of the substrate; both during the construction programme and following installation of the green roof and its irrigation system. Hot melt also provides buildability benefits during the construction project. The soft bituminous compound is self-healing, which means that any punctures during construction can be repaired before water ingress occurs. The system enables piecemeal installation to allow flexible scheduling of works at roof, terrace or podium level. It can also be trafficked soon after installation, preventing damage by other trades and allowing for breaks in the programme between the hot melt installation and the rest of the inverted build-up (for which XPS insulation is the right choice) and the green roof build-up. THE RIGHT GREEN ROOF PARTNER All these benefits make hot melt the ideal roofing system for green roof installations, but it would be a mistake to assume that all hot melt systems offer the same performance and buildability benefits. It’s vital to choose a hot melt system with a root-resistant layer specifically designed for green roofs to ensure the waterproofing is not compromised by root growth. It is also important to work with a supply chain partner that can point you to design considerations, and that can provide technical support and a service-led approach to specification. For example, at SOPREMA we are often able to help contractors save time on site by including SOPRADVANCE concrete compound in the specification, which closes the pores of the concrete to enable installation of the waterproofing system up to three times earlier than the usual 28-day wait time. The SOPREMA technical team also works collaboratively with design and construction teams to ensure the effectiveness and resilience of the roof build-up, providing the calculations, for example, which should always be based on the saturated weight of the full roof build-up to ensure it meets the maximum requirements. Ideally, specifiers should also look for a supply chain partner that can offer a specification solution for the entire roof build-up as a one-stop-shop, including structural waterproofing materials and green roof elements to ensure compatibility and efficient procurement.

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