SSQ Riverstone® Grey Random roofing slate

Its spectacular turreted and castellated tower suggests the University of Bristol’s HH Wills Physics Laboratory may have been with us for centuries rather than just eighty years. The [Sir] George Oatley designed building opened on 21 October 1927; a tribute to HO Wills, head of the Wills tobacco empire, founder of the university and its first chancellor. Standing proudly in the Royal Fort Gardens, the building’s magnificent keep-like tower is one of six planned to crown the hill.

A recently completed restoration project has rejuvenated the exterior of the Grade II-listed building, faithfully restoring the grandeur of its Renaissance-inspired architecture. Iain Martin, Director of Architecture at Capita Architecture outlines the challenge the roof provided: “It’s a broad, flat-topped mansard with dormer windows interrupting the lower pitches and with roofing slates laid in an attractive ‘random width, diminishing course’ pattern. Two different slates had been used – most were very old Cornish Delabole, probably reclaimed, and were in very poor condition with up to three-quarters of them being ‘blown’ from water damage. And there was also a small, more recent section of an unidentifiable, but possibly Cumbrian, slate.”

Random slating was once a popular method of laying roofing slates. Although needing careful setting out, it allowed different size roofing slates to be used on the same pitch. This offered a variety of benefits, magnified on a large building, as it meant that any size roofing slates could be used irrespective of whether they were being purchased new or, as was common, recovered from buildings that were being demolished. A spin-off benefit was its aesthetic appeal and in more recent years, its use to create dramatic false perspectives.

The poor condition of the slates led to four possible solutions being explored including trying to reclaim what could be saved and supplementing them with new slates but, with as many as 75% of the original slates being unsalvageable, this option really wasn’t feasible. Kevin O’Flaherty, the university’s Capital Projects Officer takes up the story: “The project team discussed the options with the conservation officer overseeing the project and it was decided to re-roof with new slates. We considered three premium-quality slates – Burlington, Delabole and Riverstone – but chose Riverstone as it was a similar hue to the originals, was the right weight, was within our budget and was readily available. With the decision made to re-roof, Camilleri & Sons, the roofing contractor involved with the project, stripped the roof back to its frame, replaced the battens and underlay and faithfully recreated the random width, diminishing course effect of the original. We’re all delighted with the result!”

SSQ Riverstone Grey is a premium-quality roofing slate produced exclusively by SSQ at its La Florida Quarry in the San Luis region of central Argentina. Riverstone is actually a phyllite, a rock similar to slate and shares its essential characteristics but surpasses its qualities: it’s stronger and more resilient than most slates, and has a pleasing medium-grey colour with a subtle green tinge. Its quality and appearance has led to it being approved as an alternative to indigenous slate by many of the UK’s principal conservation agencies including English Heritage, Historic Scotland, Cadw and both the Brecon Beacons and Snowdonia National Park Authorities. SSQ Riverstone Grey roofing slate is available in a range of sizes and can be provided in either Mixed or Random Width pallet loads specifically for use as Random, Random Width or Random Width in Diminishing Courses slating.

For further information about SSQ Riverstone Grey Random roofing slate, or to receive the latest copy of Slateworks, SSQ’s quarterly newsletter, please contact SSQ on 020 8961 7725 or via

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