Latest NFRC Technical Publications-Oct 2026

GN78 GRP Chimneys and Dormers - Compliance and Performance Issues

NFRC Members and the NHBC have reported a significant number of failures and claims associated with Glass Reinforced Plastic (GRP) chimneys and dormers. 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 has been developed to highlight some of the principal issues so that contractors can advise their clients of the potential risks associated with weathering to GRP chimneys and dormers.

GN85 Efflorescence on Concrete Roof Tiles

The appearance of white deposits or streaks on a newly constructed or recently re-roofed property can understandably cause concern. One of the most common enquiries received by NFRC relates to these white marks, often leading homeowners to question whether their roof has been incorrectly installed or whether the roof tiles are defective.

This guidance has been developed to explain what efflorescence is, why it occurs, its effect on the performance of a roof and when further investigation may be appropriate. It applies to concrete roof tiles, explaining the characteristics of efflorescence and provides general information for homeowners and building owners. It does not replace a site-specific inspection where there are concerns regarding the performance or condition of a roof.

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NFRC Members should access the version that is listed as "included in your membership".