22 CONTEXT 185 : SEPTEMBER 2025 Slope 3 had been raised and reslated with slightly thinner and larger slates from a larger and deeper quarry, but they were still random sized. Slopes 5B and 6. Random slating on Slope 6, as on Slopes 3 and 4. The formerly random slating on Slope 5 had been changed to thin large slates, centre nailed. The earliest slating on Slope 2 and the valley and reslating on Slope 1. By this time the early slating had deteriorated and been ‘repaired’ with cement mortar. sizes and sold by weight, sufficient to cover a given roof area. Typically in Lleŷn, they would include a few courses of 16- or 14-inch-long slates, with the rest of the roof 12- and 10-inch, all with a narrow range of widths. Slopes 3, 4 and 6 illustrated how slates changed as the quarries became larger and deeper. They also showed how the quality of slaty cleavage improved, how they produced thinner, slightly smoother and larger slates, but still with a modest output and so still sold in random sizes. The slates were still peg-hung on riven laths and torched. By the 19th century, quarries and mines had become very much larger and deeper, and production had expanded to the extent that slates could be sold in single sizes (tally slates of a uniform, single size, sold by count rather than as random slates sold by weight). These large, thin slates are more susceptible to wind uplift than small, thick slates. This resulted in a change from peg hanging or top nailing to the more wind-resistant centre-nailing system. This type of slate had been used to reslate Slopes 5 and 9–11, double lapped and centre nailed. Slate supply As many slates as possible were reused. Where new tally slates were needed to make up a shortfall, they were obtained from Welsh Slate Ltd in appropriate colours: heather blue from Penrhyn, and grey from Cwt y Bugail quarries. Random slates were made on site by WJC using block from the same quarries. When the existing tally slates on Slope 1 were originally made, the width variation was greater than the standardised The roof in 2022. The red areas were random slates, and the black were tally slates (slates of a uniform, single size). Before slating commenced, Building 7, a recent store shed, collapsed and was abandoned.
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