Welsh Slate

The slate industry began in North Wales during the Roman period (slate was used to roof the fort at Segontium, now modern Caernarfon). The industry grew slowly until the early18th century, although records exist of slates being commercially sold and shipped to Ireland as far back as 1413. Indeed, in 1980 a shipwreck dating from 1272 was found in the Menai Straights. It was full of Penrhyn roofing slates which were intact and unaffected by their seven hundred years immersion in salt water.

Welsh Slate has a long association with Ireland and was used to roof much of the country. By the late 1500s over 100,000 slates were exported from Wales to Ireland every year. By the late 1600s, this number had increased 10 fold to over 1 million slates per year. Slates shipped to Ireland were traditionally known by the name of the port from which they were exported. Llechwedd and Ffestiniog slates were known as Portmadog slates, slates from the Llanberis Valley were shipped from Port Dinowic, Nantile slate were shipped from Caenarfon, and Penrhyn Heather Blue slates shipped from Bangor were known as Bangor Blues.

At its peak in the late 19th century, the slate industry employed over 20,000 workers. In recent years it has experienced a renaissance, following the acquisition of three main quarries by Welsh//Slate, a company owned by Lagan Building Solutions.

Traditionally Welsh slates were cut to uniform sizes 24" × 14", 24" × 12" and 20" × 10". They were sold usually in single size slates, although because they were hand split along their lines of natural cleavage they came in a variety of thicknesses. In later years they were sub-divided into grades such as Bests, Standards, Heavies, Strongs. These names changed over the centuries. In the mid 1990s with the award of the BS Kitemark, the name Capital was used to describe a Welsh Slate with a nominal thickness of 6mm and County for Welsh Slates 8mm thick. Towards the end of the 1990s the name Celtic was introduced to describe a 10mm thick Welsh Slate.

In 2006 Welsh // Slate invested £6 million in a new manufacturing process for its roofing slates. The new facility uses multi-blade saws to produce sawn roofing slate, increasing yield and reducing wastage. This process produces up to 300,000 roofing slates per week with an even tighter dimensional tolerance than hand split slates. This, combined with the slate's sawn back, reduces the need for sorting and grading and significantly reduces costs. The resulting slates set the benchmark to which all other roofing products aspire.