GN78 - GRP Chimneys and Dormers - Compliance and Performance Issues

Glass Reinforced Plastic (GRP) chimneys and dormers are increasingly specified on new-build developments as lightweight alternatives to traditional construction. However, NFRC members and the NHBC have reported a significant number of failures and claims associated with these products. In many cases, the manufacturer’s installation instructions conflict with British Standards and recognised industry good practice. This creates a situation where installers cannot achieve a compliant or durable installation, and long-term performance could be compromised. This guidance note highlights some of the principal issues so that contractors can advise their clients of the risks associated with weathering to GRP chimneys and dormers.