The National Federation of Roofing Contractors (NFRC) has recently published new guidance warning about the risks of using Brazilian metalutite, often marketed as “Brazilian slate”. The document, GN66: Brazilian Stone (Slate),  makes it clear that this material is not a true slate, but a different type of rock called metalutite with weaker properties and a shorter lifespan.

For years, many in the roofing trade have reported issues with Brazilian slate, from cracked tiles to roofs that simply don’t last. Now, the NFRC guidance confirms these concerns, noting that Brazilian metalutite is “more brittle than European slates” and should only be used with hook fixings to reduce the chance of breakage.

What’s the Difference?

True slate, such as the CUPA PIZARRAS’ tectonic slate used across the UK and Ireland, is a metamorphic rock is a product of intense geological forces, giving it exceptional strength, consistency, and resistance to water and frost. It’s a material proven to perform for over a century, offering both beauty and durability that man-made or lower-grade alternatives simply can’t match.

For roofers, that means fewer call-backs and a reputation built on quality work. For homeowners, it means peace of mind and a roof that looks stunning for decades.

By contrast, Brazilian metalutite comes from mudstone, a sedimentary rock that hasn’t gone through the same geological transformation. As a result, it’s far more likely to:

• Break or delaminate during handling or installation
• Absorb water and suffer frost damage
• Have inconsistent thickness and surface quality

Real Risks for Roofers and Homeowners

These weaknesses can lead to early roof failures, costly repairs, and frustrated customers. In fact, the National House Building Council (NHBC) stopped covering Brazilian metalutite under its warranty back in 2012 due to reliability concerns.

Steve Pearson, UK Director at CUPA PIZARRAS, commented:

“With a unified industry position on this topic, contractors and specifiers can make informed decisions based on geological facts and the associated risks of using metalutite products. Clear industry guidance protects everyone – from roofers working with reliable materials to homeowners investing in roofs that will truly last.”

To learn more about the NFRC’s guidance and the geological differences between Brazilian metalutite and genuine tectonic slate, visit: Brazilian Metalutite Risks – CUPA PIZARRAS