GRO (Green Roof Organisation) Code of Best Practice 2021

The GRO code provide principles and design criteria for high quality biodiverse green roofs. It explains how to meet the standard for a biodiverse green roof, with a substrate depth varying between 80 and 150 mm, planted with a diverse mix of native wildflowers and sedums, and with the addition of biodiversity features such as dead wood, rocks or water features. This will deliver optimum benefits for flood mitigation, biodiversity and climate resilience.

It is important to meet this standard, because low quality green roofs are often simply a thin sedum mat unrolled onto a roof. These will offer little biodiversity benefit, little flood reduction and heat reduction, and are not resilient to drought and heatwaves.