24 (" MACDUFF") • ••• (" BALLACHULISH") /1 ~--¥..,,_ AND £./ (" EASDALE" ) (;7 ~ T ~ LAND • • • • • HIGHLAND BOUNDARY {J • • (" ABERFOYLE") ~ • • Q' •• • • SOUTHERN UPLANDS.,/ Scottish slate quarries: Map by Historic Scotland Architect, Dr Michael Burgoyne, who carried out initial research into Scottish slate for the agency. inevitably leading to diminishing stocks. Theft of slates from restorable buildings -even from occupied buildings -is increasing and, 30 years since production ceased, supplies are beginning to dwindle to a critical level. In recent years, there has been a return to the use of natural slate on both existing and new roofs, reflecting its expected long life by comparison with most other materials, and demand for slates is increasing. Surprisingly, the price of second-hand Scottish slate remains competitive as compared with new Welsh or Cumbrian slate and can even match the low-cost slates being imported from Spain, Portugal, South America, and even from as far afield as China. However, none can so far match the appearance of Scottish slate and there are questions about the durability of some of the substitutes, too. Unless quarrying is revived soon, an important part of the character of Scottish townscapes will be lost. Cheaper alternative materials, resin based and fibre cement replica slates and concrete tiles which purport to emulate natural Scottish slate, will take over and the special slating skills will be lost. STANDARDS FOR TRADITIONAL MATERIALS? An added problem for Scottish slate, as for some other traditional building materials, is that they have never been covered by adequate standards. The main standard for slates, BS 680: 1944 Roofing slates, was based originally on traditional Welsh standards and defined a type of slate to meet the demands of the growing industrial centres of England: Single sized, 'tally', slates (identical slates which were sold by a tally or count of 1,000) as large and thin, as possible, made for cheaper transport and easy laying and provided maximum coverage of low-pitched roofs constructed from minimal amounts of timber. The tests for water and acid resistance included in the British Standard were developed merely to ensure that such slates were suitable for use in the damp, polluted atmosphere of postwar London. Similarly, BS 5534: Part 1: 1990, British Standard code ofpractice for slating and tiling referred in the main to English slating practice, using battens and underslating felt, rather than Scottish, where sarking boarding takes the place of purlins and battens, and felt is often omitted. In fact, the Code specifically discourages fixing slates direct to boarding (section 23.3). However, by acknowledging (16.5), that "Consideration should be given to the best local practice and to any form of treatment that may have been developed to deal with special conditions ... " the irrelevance to Scotland of much of the standard is clearly implied. There is at present no alternative guide to Scottish slating, which is surprising, since it offers practical advantages. For example, the traditional method of fixing Scottish slates, which are single nailed at the head, aids maintenance since, to replace a damaged slate, neighbouring slates can simply be 'swung' aside and the new slate nailed in place. As far as Scotland was concerned, such standards only ever provided a crude baseline. It is customarily acknowledged that, with more rain and snow and considerably higher windspeeds to cope with, Scottish roofs require heavier slates and different constructional detailing. Neither do the current standards recognise the possible advantages which Scottish slate may provide in terms of strength, hardness and durability. When the new European slate standard is agreed in the next few years, it is to be hoped that it will be based on a radical re-think of the current standards to provide for traditional Scottish-style slates and slating. This could offer other environmental benefits. The demand for standard rather than random sizes, for example, has made the modern slate industry proverbially wasteful of what is, after all, a finite resource: currently a mere 8-10% of the material extracted is made into roofing slates, sometimes much less. The waste is further increased when extraction by blasting is used, as it still is in some working quarries, rather than sawing. CONTEXT 52
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