RECYCLING LECA CLAY FROM GREEN ROOFS


Leca aggregate was removed during roof renovations of a commercial building in Helsinki, and then used, after further processing, as roof soil for green roofs.

Leca aggregate was removed during roof renovations of a commercial building in Helsinki, and then used, after further processing, as roof soil for green roofs.

Leca aggregate, produced through the burning of natural clay, is a fully recyclable material.

"In roof renovations, the old roof is dismantled and a layer of Leca aggregate, on average  400 mm thick and acting as heat insulation, is removed and delivered as a raw material for use in roof soil. A vapour barrier is installed onto hollow-core slabs, as well as Leca aggregate and 250 mm mineral wool. Leca aggregate ensures adequate ventilation of the roof and it is convenient to carry out inclinations leading to roof drains,” says Lasse Ruuskanen from Eristysmestarit Oy, supervisor for the renovation of a commercial building located in Herttoniemi, Helsinki.

Leca aggregate is removed from the roof and transported away by Anpe Oy.
 

Recycling to save on costs and to protect nature

"The share of recycling in turnover is growing all the time and is at 7−8 percent when it concerns Leca aggregate. Of recycled Leca aggregate, about 80 percent is used in earthmoving and 20 percent for other uses. For example, the processing value of Leca aggregate and soil in the manufacturing of roof soil for special use will rise with no generation of waste,” says Hannu Pesola, ANPE Oy's managing director.

Pesola reminds us that Leca aggregate combined good properties, namely light weight, compressive strength and good thermal insulation properties are retained, even when the product is re-used.

"By taking advantage of Leca aggregate removed from roofs in earthmoving or other use, one can reduce the need for new light aggregates in such applications, whereupon the capacity of a lightweight aggregate plant will improve and materials and the environment will be saved”.

Supplying water to help nourish growth

Leca-aggregate removed from a roof is delivered to Ralf Ajalin Oy’s  Pihamaa service and soil station in Vantaa.

"Leca aggregate is crushed and it is used as an important part in the manufacture of roof soil. Compared to normal soil, roof soil as a product has been processed for longer and is a more valuable specialty product," says Olli Mannerjoki, from Ralf Ajalin Oy, responsible for Pihamaa-service products.

"Crushed Leca aggregate allows the soil to be much lighter, so that roof structures are not placed under excess loads. The main tasks of Leca aggregate in roof soil are to make the soil light, as well as to improve the movement of water in the growth base, which facilitates access to water for plants".