Natural slate

NFRC highlights risks of Brazilian metalutite as a roofing material

nfrc guidance note post uk

The National Federation of Roofing Contractors (NFRC) has published Guidance Note GN 66 addressing the use of so-called ‘Brazilian slate’. The document warns that this material presents “certain characteristics” which may “reduce the longevity of the roof.” 

These conclusions reinforce what independent geologists and industry experts have long emphasized: Brazilian ‘slate’ is actually a metalutite, a sedimentary rock that has not undergone full metamorphism.  

The full document is available to read here (access restricted to NFRC members) : NFRC GN66 Brazilian Slate. 

The NFRC highlights several practical consequences and potential risks associated with the use of Brazilian metalutite on UK roofs: 

  • Its high water absorption makes roofs more vulnerable to frost damage. 
  • Its increased brittleness raises the risk of breakage and delamination. 
  • It has a significantly shorter lifespan compared to tectonic European slates. 
  • Its environmental footprint is higher due to longer transport routes. 

These warnings align with concerns that experts across the industry have been voicing for years. Recently, the Cluster da Pizarra de Galicia (Spanish Association of Slate Producers) published an in-depth analysis on the subject, which can be read here: Brazilian Metalutite: Risks and Differences Compared to Natural Slate .  

Ultimately, GN 66 is a reminder for the industry to prioritize durability, authenticity, and transparency. For roofers, specifiers, and homeowners alike, understanding the differences between true natural slate and materials such as Brazilian metalutite is essential to making informed choices based on facts rather than marketing labels. 

 

interview iconWe’re here to help you make the best choice for your roof. Whether you have questions about Brazilian metalutite or want advice on the natural slate that suits your project, our experts will get back to you as soon as possible.