NFRC Unveils Updated GRO Code for Green Roofing

Supported by The National Federation of Roofing Contractors (NFRC) – the UK’s largest roofing trade association – the Green Roof Organisation (GRO) has unveiled a new and updated GRO Code for green roofing. The revised code is designed to provide assistance for anyone who is involved in the design, specification, installation or maintenance of a green roof.

First published in 2011, the GRO Code is intended to be a code of best practice and to serve as a guide for behaviour and standards relating to all matters in green roofing. This latest update contains more detailed information on meeting the requirements of the London Plan Policy, together with added guidance on substrate installation and waterproofing.

The revised GRO Code reflects the growing movement by councils and local authorities throughout the UK, including the London boroughs, that now expect green roofs to be designed for new developments, where feasible. As such, it provides an enhanced ‘Living Roofs and Walls’ technical report supporting the London Plan Policy that was first unveiled in 2008. This document provides guidance in helping London combat the effects of climate change and recognises that green roofs have the potential to improve London’s resilience to climate change by reducing storm water run-off velocity and volumes, and by increasing the cooling effect during London’s hotter summers. They also bring many other wider environmental benefits.

Regarding green roof substrate installation, the GRO Code provides guidance on the size of substrate sacks required for certain projects and states that they should be disposed of once the substrate has been discharged at roof level. The method choice of lifting substrate up to the roof level, and its subsequent dispersion of it across the roof, has significant access, budgetary and scheduling implications and is subject to the size of project. Substrate should be applied to the required depth (including the appropriate settlement volume) using grading bars. Depth checking should be undertaken throughout the installation. Once the green roof is installed it should be saturated to capacity using suitable temporary irrigation equipment prior to on-going temporary irrigation depending on time of year.

When it comes to waterproofing, the revised GRO Code now states that in all applications the primary waterproofing layer is critical to the successful performance of the roof as a whole, therefore its function and performance characteristics, and its suitability for use within a green roof system must be assured. At a minimum the specified waterproofing system should be certified to FLL Guidelines against root resistance and/or be covered by British Board of Agrément (BBA) Certification for green roof applications. A wide range of waterproofing options fall within these requirements including reinforced bitumen systems, hot melt monolithic systems, single ply systems, liquid applied systems and standing seam aluminium systems. Guidance is also provided on waterproofing inspections.

Commenting on the latest GRO Code, Simon Poe, Business Operations Director at Alumasc Roofing and a member of the GRO Advisory Technical Group 2013 said:

“Research has indicated that green roofs respond differently to the environment in which they are installed. UK green roofs will therefore perform best if they are tailored to the environment in the UK.

The publication of the inaugural GRO Code in 2011 was a positive first step in the pursuit of good practice in the design, supply, installation and maintenance of UK green roofs.”

Simon adds: “The new edition of the Code demonstrates the industry’s desire to further enhance the quality of green roofs in the UK. The Code informs the decisions of professionals that specify, manufacture, install or maintain green roofs through broader and more detailed guidance. In future, the Code will underpin further enhancements; leading towards an ultimate ambition of prescribing acceptable ranges of performance for components on a quantitative basis.”

Ray Horwood CBE, Chief Executive of NFRC concludes:

“Green roofs perform a vital role in helping cities adapt to the effects of climate change. However, green roofs can only provide these environmental benefits if designed and installed in a way that ensures that minimum performance criteria are met. This code therefore highlights the important green roof design, installation and maintenance considerations and provides guidelines as to how they can be accommodated in the final green roof scheme.”

GRO was founded circa 2008 and represents a partnership of industry (green roof manufacturers and installers) and stakeholders, coming together to develop guidance for the specification, design, manufacturing, installation and maintenance of Green Roofs. The first publication was the GRO Guidelines in 2009, followed by the GRO Code in 2011.

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