As one of the world’s oldest roofing materials, natural slate sits proudly atop of many of Britain’s historic buildings and housing stock. Due to its amazing durability, which can often outlast the actual buildings themselves, many of these roofs have simply weathered with age over the years and require minimal repair and maintenance to restore them to their former glory.
The charm of repairing or replacing a traditional slate roof can sometimes fade when faced with sourcing like-for-like slates. Specifiers and contractors alike are often faced with various dilemmas: for example; it could be that the slate which adorns the roof is no longer available, or perhaps the roof needs extending and an exact match can’t be found. Alternatively, the building may be listed – which means that its original character must be maintained – and this can prove challenging if the replacement slates don’t come anywhere near to matching the original slate.
Older buildings with Scottish slates laid in diminishing courses present one of the biggest predicaments for specifiers and contractors. Slate is one of Scotland’s oldest and most significant building materials, and during the 18th, 19th and early 20th centuries, over 200 quarries produced a wide variety of types and colours. Today, Scottish slate graces many historic buildings and conservation areas, yet sadly, the last slate quarry in Scotland ceased production in 1955.
In general, Scottish slate is coarser-grained than other slates and, as a result, it is thicker and more irregular than its Welsh counterparts, for example. This distinctive appearance has resulted in random sized slates of differing thicknesses laid in diminishing courses, which gives Scottish roofs their distinctive and cherished look.
Such has been the eagerness to source slates that retain this Scottish look, that over the years, the same slates from old buildings were stripped in order that Listed buildings could be preserved – not a very satisfactory conservation equation and the wastage factor meant that two or three roofs were regularly required for every re-roofing project. Attempts to re-open a Scottish slate quarry have not, so far, been successful and future prospects deem it unlikely.
So, what are your options when repairing or replacing a Scottish slate roof? You could try to re-use the slates, although you may lose in excess of 50% in the process. To make up the difference, you will need to find a supply of matching second-hand slates. Not only is this becoming increasingly difficult, not to mention costly, the chances are that you will end up with a roof that looks somewhat second-rate. That’s because the smaller slates will be too small, and a proportion of the slates will be not quite up to the same standard.
As time passes, supplies of good quality second hand slates are increasingly difficult to source, thus making it necessary to rely on non-Scottish slates. However, some slate, such as Spanish and Chinese, tend not to be suitable, both in terms of appearance and/or durability.
Lastly, you could consider a ‘new’ slate that matches as closely as possible the colour and dimensions of the original Scotch slate. Supplied by SIGA Slate, in conjunction with Welsh Slate, a new Welsh blue/grey slate – SIGA 120 – is being quarried to replicate the diminishing courses on the traditional Scottish roof. Cwt y Bugail quarry is currently producing a range of sizes – varying in length from 400mm, down to 300mm at 25mm intervals, and in width from 375mm, down to 200mm, also at 25mm intervals. These are roughly equivalent to those produced in Scotland’s Ballachulish Quarry in the 19th century and still found on countless roofs today.
Although the new slates are not truly random, the change from one size to the next is not readily apparent. Likewise, although paler than the original Ballachulish slate, they will darken with age and blend in with the original material. Their cost is, to an extent, mitigated by the reduction in time taken to sort through, trim and size second hand slates, and for the building owner, the assurance that a re-slated roof will endure for generations to come is also invaluable.
Fully traceable, and with a quality standard that second-hand slate could never hope to match, these new slates are fast becoming a popular alternative to the most commonly used Scottish slates. At last, the market has a viable solution for restoring and preserving the beauty of traditional Scotch slate roofs, and Scottish heritage is thankfully being reclaimed at last.
For more information on SIGA Slate please call our Technical team on 01480 466777.