The green credentials of two new apartment buildings in London were substantially enhanced with large green roof planters constructed on the external mezzanine walkways. Traditional soil would have created structural weight concerns so contractor Ground Construction Limited of St Albans, Hertfordshire selected the lightweight advantages of Leca® Lightweight Expanded Clay Aggregate as the growing medium for these attractive features.
Leca® Lightweight Expanded Clay Aggregate is a free draining, lightweight aggregate created by heating and firing natural glacial clay in a rotary kiln at up to 1150°C. This process transforms the clay into lightweight ceramic granules with a hard shell and porous core. The material is extremely light with a bulk density of just 0.3 tonnes per cubic metre. The granules are frost resistant and chemically inert, ideal for horticultural planting.
The close confines of the construction site for these new apartment blocks in Bermondsey, South East London made access to the giant planters difficult and the problem was compounded by restricted hours of access. The choice of Leca® Lightweight Expanded Clay Aggregate 10-20mm provided a package of beneficial solutions.The 55m³ of material required for each planter was blown pneumatically through a 30 metre long, flexible pipe from the Leca® Lightweight Expanded Clay Aggregate delivery vehicle directly into the planter in a matter of hours, thus removing the handling, access and timing problems at a stroke.
The high volume, low weight attributes of Leca® Lightweight Expanded Clay Aggregate significantly reduced the weight loading on the deck structure. The horticultural benefits of the material resulted in the establishment of a fine display of environmental green roof planters on the site for the enjoyment of residents and visitors.
“Leca® Lightweight Expanded Clay Aggregate proved a very good solution for our green roof planter project at Bermondsey,” reported Sean Conroy, Buyer for Ground Construction Limited. “There was no heavy handling, no spillage during the load up and no dust blowing around so the site was clean by comparison with traditional soil fill and the transportation of it. We had fitted a watering system into the planter before we loaded the Leca® Lightweight Expanded Clay Aggregate and the plants will be putting on a great show this season.”