Richard Sabin, Director of Biotecture: “Working with Grodan gives us the reassurances we and our customers need”

“We saw huge potential in vertical landscaping, but we immediately faced a challenge in terms of finding the right growing media for that. Soil would be too heavy and get too saturated, not leaving enough airspace for the roots. We considered lightweight expanded clay aggregate – also known as LECA – as an alternative, but realized that it was too loose to hold up vertically,” he continues. “Then one day, we read about Grodan in an interesting article about Scandinavian roof gardens, so we reached out and arranged a demo at our offices. When the Grodan representative poured a bottle of water on the strip of stone wool he was holding and it retained it all, we instantly knew that it was the right solution for us.”

Grodan ticks all the boxes

That strip of stone wool was PP100, a little-used Grodan product that had been specifically developed for use on roofs. “It is almost four times as dense as most single-use stone wool. This means that it has sufficient inherent structural strength and dimensional stability to be incorporated into our panels as a fundamental engineering product,” explains Richard. “This ensures that our customers can depend on a robust, compliant and fully validated living plant system that is suitable for use on the outside of buildings.”

“Secondly, stone wool is chemically inert, which enables us to provide the optimal cocktail of nutrients for the plants. Another benefit of it being inert is that, if we do suffer with any pests or diseases, they are always in the plants or roots rather than in the stone wool, so we can treat them, flush them out and still reuse the Grodan growing medium,” he adds. “And thirdly, even when stone wool is fully saturated, it still provides enough airspace for roots to exist. As a result, we’re able to create a resilient growing space to permanently support robust, thriving plants outside of buildings, despite living walls being a technically, horticulturally and hydraulically challenging environment.”

^{Recently completed living walls at the McArthurGlen Paris-Giverny Designer Outlet}

Patented panels

These characteristics of Grodan’s stone wool enabled Biotecture to develop its own patented BioPanels. These modular panels are made up of the plants in the Grodan growing medium, separated by capillary breaks to maintain the hydraulic balance, backed by aluminium rails and a dripline, then a rear drainage layer, a waterproof backing board and a support system, with a panel box holding it all together. The panels are then stacked on top of one another to create a wall.

^{BioPanels, containing the customized, pre-dimensioned Grodan growing medium, ready to be planted up in Biotecture’s nursery}  

Dedicated nursery facility

Biotecture has its own 4-hectare dedicated nursery facility where it raises upwards of half a million plants a year for use in its living walls. “We buy them as plug plants from the Netherlands, then grow them to exactly the right tray size so that we can ‘plug and play’ them straight into our panels. We grow them on Grodan granulate so that the roots don’t suffer any substrate shock when they’re transferred into the panels,” explains Richard.

The panels containing the plants are then ‘pre-grown’ in the greenhouse, positioned on over 3,000m² of purpose-built vertical racks, for around eight weeks before being shipped to customer projects. Most of those projects are in the UK, and include many high-profile sites such as No. 1 Court at Wimbledon. “But we also work with plant growing partners in other countries such as Germany, the Czech Republic, Dubai and the USA, which allows us to complete projects internationally,” he comments.

^{Richard inspecting a living wall growing in Biotecture’s West Sussex nursery}