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Robin Kent discusses progress in
re-incarnation of the Scottish slate industry
and Scottish slating practice


TRADITIONAL BUILDING
MATERIALS: SCOTTISH SLATE
The appeal decision earlier this year requiring the use of Welsh slates, in- stead of the Brazilian or Spanish alternatives offered, for reslating scheduled monuments in the Royal William Yard, Plymouth, has highlighted some of the problems facing those specifying traditional local building materials for conservation work. In his conclusions, the inspector found that only the Welsh slate met all the relevant quality standards, including colour and texture. In this particular case, the most likely original slate was still in production, but what if it had no longer been available? In Scotland, too, slate roofs are vitally important to the character of many historic buildings and conservation areas, yet the last slate quarry closed 40 years ago. To examine the problems facing Scottish slate, Historic Scotland is undertaking research and also planning a major conference on traditional materials.

WHAT IS SO SPECIAL ABOUT SCOTTISH SLATE?
Slate is one of Scotland’s oldest and most significant building materials. Throughout the 18th, 19th and early 20th centuries over 200 quarries produced a wide variety of types and colours, from four main areas: The West Coast quarries of Ballachulish and the ‘Slate Islands’ of Easdale, Seil, Luing and Belnahua; the ‘Slate Belt’ including Luss, Aberfoyle and Dunkeld; and the slate outcrops of Banff/MacDuff and of the Southern Uplands. There is documentary evidence for a Scottish slate industry from 1549 at Easdale and from the 18th century onwards Scottish slate was the main roofing material in the growing industrial cities of Glasgow and Greenock, as well as the Edinburgh New Town, now a World Heritage Site. In the 19th century Scottish slate was in demand as far afield as North America.
Scottish slate has a very distinctive appearance, making a vital contribution to the character of Scottish towns.
While the familiar Welsh, French or Spanish slate is a smooth, rectangular, regular sized slate, the top, or ‘back’, of atypical Scottish slate is usually rugged, only the underside, or ‘bed’, being smooth. As a result, most Scottish slates are ‘shouldered’, or sloped off at the top corners, to help them lie flat. While many colours can be found, the most common Scottish slates are dark grey to black, producing roofs with deep tones and strong textures. The appearance of Scottish slating is further enhanced by the use of random sizes, such that slates of varying widths are laid in graduated or diminishing courses with the smallest ‘peggies’ at the ridge. The resulting effect of exaggerated perspective increases the height and visual impact of the roofs. Such graduated, random slate roofs are a survival of the original appearance of many slate roofs elsewhere in Britain. Graduated slate roofs can still be found in Preseli in South Wales, Cumbria and Cornwall, but they were probably once as common everywhere as they still are in Scotland. Indeed, Cadw (the Welsh
sister organisation of Historic Scotland and English Heritage) is currently restoring the 16th century roof of Plas Mawr, at Conwy in North Wales, in graduated Welsh slates. Only in Scotland has this tradition survived as the norm, making possible the characteristic towers and pinnacles of Scottish baronial architecture.
Why then are Scottish slates not more widely used? The obvious answer, as above, is that they are not available. But this is far from the full story. Since the closure of the two Ballachulish slate quarries in 1955, a time when slate quarrying in the UK generally reached an all-time low, it is true that no Scottish slate quarries have been in full production. Although occasional use of a few quarries has continued, salvaged second-hand Scottish slate now predominates. Owing to the amazing natural durability of the material, which often outlasts the buildings it is placed on, supplies of slate for recycling have been maintained despite increasing demand. But demolition and redressing losses are
Scottish slating underway at Crathes Castle for the National Trust for Scotland, in 1993.
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