Historical introduction to roofs

Slate came to dominate the roofing of Wales only in the nineteenth century. Before roofing slates were mass-produced and widely distributed, there was considerable regional variety, elements of which still survive: stone-tiled roofs are still relatively common in parts of Monmouthshire and the Brecon Beacons as well as on older houses in the south Wales Valleys, for example, whilst thatch can still be found in parts of west Wales and Glamorgan. Thatching was an intensely local tradition, and different areas had their own techniques both for applying the thatch and for finishing the roof. Longstraw and combed wheat reed were the traditional materials, with a variety of underthatch ranging from straw mats in Glamorgan, to straw rope in north Pembrokeshire and Ceredigion, and heather, gorse or woven twigs elsewhere.

Although slate prevails over much of Wales, slate roofs are by no means uniform in appearance. Different quarries produced slate of quite different colour and texture and, in addition, it was only from the later nineteenth century that uniformly sized machine-cut slate became ubiquitous. Early slate roofs used hand-cut slates in a variety of sizes laid in diminishing courses with the thicker and larger slates towards the bottom of the roof. Methods of fixing also varied, and in earlier roofs, slates were hung on wooden battens using wooden pegs in a single hole at the top of the slate. Later roofs were more often centre-nailed with two holes.

Roofs of small slates bedded in lime mortar are a distinctive feature of the western seaboard. Sometimes these roofs were also grouted with lime mortar (and later with cement) as a repair technique. In some areas, by contrast, there are roofs of very large slates. Local variations reflected what the builder could afford, and continue to add to a sense of place.

Other important distinctions lie in the details of finish. The treatment of valleys within the roof varied, as did handling of the ridge. Interlocking ridge tiles were often used on stone-tiled roofs, and the technique was sometimes translated into slate. Mortared ridges were also used, but, from the mid-nineteenth century, fired clay ridge tiles were mass-produced and widely available. Plain clay tiles for the body of the roof were also produced, but were never widely used in Wales until the twentieth century.

Another product of the industrial revolution was corrugated iron. It came into use in the mid-nineteenth century and made its appearance in domestic building primarily as a substitute for failing thatch, and was used as the original roofing (and walling) material relatively rarely. It has some claim to be considered as a traditional building material, and even has something of a regional distribution.

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