London’s highest all-weather garden made possible with plastics

Nylon components and ETFE film are providing London's highest all-weather garden with both a cost-effective and weight saving solution that will give visitors protection from the elements as well as a clear view.

The materials are being used in the form of 3D printed transitions and transparent film cushions for a rooftop garden situated above the new ‘6 Bevis Marks’ office building in the heart of the capital’s business and finance district.

The 400 sq. m garden is protected by a baldachin made of transparent film cushions extruded from 3M Dyneon Fluoroplastic ETFE (ethylene-tetrafluoroethylene) by a Germany-based processor, Nowofol.

The ‘NOWOFLON ET 6235Z’ films made from Dyneon ETFE are highly transparent, meaning that visible light and UV-A radiation – which is important for plant growth – to pass through. The film also has an extremely high resistance to chemicals, including the pigeon droppings ever present on London’s roofs.

The material is so smooth that a normal rain shower is sufficient for effective cleaning, says 3M, meaning the operating costs over the entire lifetime are significantly lowered.

The weight per unit area of the roof is just one twentieth of that of glass. This was a strict requirement of the architect, Fletcher Priest, as the new office building – which is a conversion from an existing 1980s structure that was only half the size – still uses the original foundations.

Components manufactured using 3D printing

Skanska UK, based in Rickmansworth, Hertfordshire, designed and manufactured the support structure for the garden. The structure consists of eight hollow columns with a diameter of 355mm, with up to seven additional support arms projecting from each to create a ‘tree-like’ shape to support the film canopy. 

The transitions from the columns to the support arms were produced using 3D printing from architectural nylon, to create a smooth finish. This is thought to be one of the first construction applications to use 3D printing for structural components.

The 4x4 metre film cushions inserted in the steel structure were made up by London-based Vector Foiltec - a specialist in structural film construction. The company uses a Texlon ETFE cushion system, which gives a high performance, long-life building envelope designed to cope with high wind and snow loads.

The tensile strength of films made of Dyneon ETFE can reach 50 N/mm² and the elongation at break is more than 300 percent. Over more than three decades, 3M says the material has proven to be “extremely durable and resistant” in all climatic zones.

Rated “Excellent” according to BREEAM

With regards to sustainability, the 6 Bevis Marks building has achieved an “Excellent” rating according to the widely used BREEAM certification system.

Contributing to this overall rating is the film cushion for the baldachin, as the Texlon System used to produce it has been certified with the world´s first Environmental Product Declaration (EPD) for transparent building skins.

Also, thanks to the overall low weight of the film canopy the support structure was able to have a much more slender and resource-saving design than if glass was used in the design. On top of that, additional sustainability credentials were earned as Dyneon ETFE requires no softeners during production and is completely recyclable.

Image: The stunning rooftop structure