In order to minimise loading on the new structure, Leca® LWA was used throughout the site to form new green roof landscape features.
In order to minimise loading on the new structure, Leca® Lightweight Expanded Clay Aggregate geotechnical fill was used throughout the site to form new Green Roof landscape features.
Working on behalf of construction partners Laing O’Rourke and landscape architects BDP, Willerby Landscapes Ltd of Kent – who have previously widely used Leca® Lightweight Expanded Clay Aggregate within green roof gardens for planters and general landscaping – selected the Leca® Lightweight Expanded Clay Aggregate not only for its lightweight and free draining properties, but also its ease of installation .
As the Leca® Lightweight Expanded Clay Aggregate is rounded, the friction between each pellet makes the material much easier to mould into landscape shapes than some other lightweight materials.
At only one seventh the density of traditional crushed fill and freer draining than soil, the Leca® provided a lighter, easy to handle solution for Willerby Landscapes. Leca® Lightweight Expanded Clay Aggregate was used in conjunction with proprietary drainage matting and block polystyrene to form new green roof features at the centre of the development. The fill was also used within feature raised floral beds where the material will assist in the retention of moisture within the soils to feed the vegetation during dry periods.
The original green roof design for the scheme included greater use of polystyrene, but a cost comparison and the various advantages of Leca® Lightweight Expanded Clay Aggregate when used as an intermediate fill, led to its specification.
The free-draining nature of Leca® Lightweight Expanded Clay Aggregate also assists in the eco-friendly plan to recover water during wet weather, then recycle it for irrigation of the parkland in dry spells - ideal for green roof design.
Additionally, as part of the water attenuation scheme for the whole site, excess water is harvested from the parkland into giant tanks for controlled release into the nearby Mersey.
John Melmoe, of Willerby Landscapes commented: “We have used Leca® LWA extensively on previous projects, including roof gardens, and it performs extremely well. It doesn’t have any adverse effect on waterproof membranes because it is rounded and does not puncture them.Together with the weight advantage, this makes it an all round cost-effective material to use.”
An estimated 9,000m³ of Leca® Lightweight Expanded Clay Aggregate was used during the project, which was completed in spring 2008, as the city celebrated its year as the European Capital of Culture. The park, shopping complex and car park is now fully operational and encompasses some 46 individually designed buildings providing some 200,000m² of shopping, including many of the major names in UK retail.