Slate Roofing/Cladding
Natural roofing slate is a fine-grained metamorphic rock formed from mudstone or shale under tectonic compression, characterised by its distinctive foliation (slaty cleavage) that allows it to be split into thin, flat sheets ideal for roofing and cladding. Composed primarily of quartz, sericite (fine muscovite mica), and chlorite group minerals, slate exhibits density of 2,650-2,800 kg/m3, flexural strength of 39-60 MPa, and water absorption below 0.4% (S1 grade per ASTM C406). Slate's thermal conductivity is the lowest of common building stones at approximately 1.49 W/mK perpendicular to cleavage, and its anisotropic thermal behaviour means heat transfers over 2x faster parallel to the surface than through its thickness — making it an efficient roofing insulator. Classified A1 Non-Combustible per BS EN 13501-1 (without testing required), slate requires no chemical treatment or intensive factory processing, giving it the lowest embodied energy of all roofing materials at 0.1-1 MJ/kg. Premium Welsh Penrhyn slate carries a 100-year written guarantee, with documented service lives exceeding 200 years in the UK. In Australia, slate roofing has been used since 1829 (Captain Piper's buildings in the Rocks, Sydney) and remains the premium roofing choice for heritage homes and high-value contemporary residences.
- Pitched Roof Covering
- Heritage Roof Restoration
- Exterior Wall Cladding
- Interior Floor Tiles
- Architectural Details
Slate has been used for roofing since at least the 12th century in Wales and Brittany. The Penrhyn Quarry in Bethesda, North Wales (operational since 1770, though quarrying in the area dates to Roman times) became the world's largest slate quarry by the 19th century, employing over 3,000 workers at its peak and producing slate that roofed buildings across the British Empire. The quarry remains operational today under Breedon Group ownership. Spanish roofing slate production expanded dramatically from the 1960s, with the Galicia and Leon regions of northwestern Spain now dominating global production. In Australia, Welsh slate was first imported in 1829 by Captain John Piper for buildings in the Rocks district of Sydney. Throughout the Victorian era, slate was the standard roofing material for quality Australian construction, imported as ballast on returning wool ships. The postwar period saw slate gradually replaced by cheaper concrete tiles and corrugated metal, but heritage conservation requirements and the premium residential market have sustained demand. Today, Australian specialist slate roofing companies maintain the craft tradition, with companies like Bellstone (Sydney, est. 1991), CladCor (Melbourne), and Heritage Roofing Group continuing to install Welsh, Spanish, and Canadian slate on both heritage restorations and new builds.
DISCLAIMER: This specification document is generated from the CLAD Materials Atlas Database. Information is for general guidance only and does not constitute professional engineering advice. Values are typical and may vary by batch, manufacturer, and production run. Verify suitability for specific project applications independently.