Welsh Slate Industry

North-west Wales was the world's leading producer of roofing slate in the 19th century. Quarries in the old counties of Caernarfonshire and Merioneth, now Gwynedd, shipped slate to roofs across Britain, Europe and North America, and their techniques and workers spread the industry to other countries.

Early history

Slate roofed the Roman fort of Segontium at Caernarfon. The Cilgwyn quarry in the Nantlle Valley is thought to date from the 12th century and to be the oldest in Wales, and the first record of quarrying near the later Penrhyn quarry is from 1413. A small export trade to Ireland existed by the late 16th century, and in 1713 fourteen shipments carried 415,000 slates to Dublin.

Industrial growth

Between about 1730 and 1740 standard sizes were introduced, with aristocratic names. The largest, the Duchess, measured 24 by 12 in (610 by 305 mm), followed by Countess, Lady, Double and Single sizes. Large estate quarries opened in the late 18th century:

• Penrhyn, near Bethesda, developed by Richard Pennant from the 1770s and greatly expanded from 1782;
• Dinorwig, near Llanberis, worked commercially from 1787.

Canals, tramways and railways, such as the Padarn Railway, carried slate to the coast. Exports to the United States grew after a 1794 coastal tax, and Germany became an important market after the Hamburg fire of 1842.

Peak and decline

Welsh production peaked at over half a million tons in 1898, when about 17,000 men worked in the industry. The industry was then hit by a recession from 1879, the Penrhyn dispute of 1900-1903, competition from tiles and imported slate, and two world wars. Output fell from 54,000 tons in 1958 to 22,000 tons in 1970, and by 1972 fewer than 1,000 men worked in North Wales slate.

Legacy

Welsh slate shaped the look of British towns and encouraged the shallow-pitched roofs of Georgian architecture. In 2018 it was designated a Global Heritage Stone Resource, and in 2021 the Slate Landscape of Northwest Wales was inscribed as a UNESCO World Heritage Site. Penrhyn is still worked today.