Natalie Bushell, Glasgow Caledonian University: MSc Environmental Management
The Scottish slate industry used to be world- leading, with slate quarries at their peak in 1896 producing some 45,000 tonnes (45 million slates).
By 1910 this output almost halved. By the 1960s all Scottish quarries had closed. Now concrete tiles or imported slates are increasingly used for replacements or repairs.
Natalie, a Traditional Building Materials trainee and Geology graduate, gained a strong interest in this forgotten industry. The project initially arose from working with Historic Environment Scotland and looked to research the environmental benefits and costs of re-roofing Scottish traditional buildings (and roofing new builds) in slate and comparing this to the alternative products over the lifetime of the building. GIS was used to identify and quantify the amount of Scottish slate roofs to estimate the amount of slate that would be required for eventual repairs.
The project also compared the carbon footprint of imported slate to slate that could be sourced from old Scottish slate quarries, which would support the environmental case for Historic Environment Scotland to reestablish and research solutions to make a renewed Scottish slate industry more environmentally friendly and desirable.
The Scottish slate industry shut down over 60 years ago so there is currently no supply of new Scottish slate tiles and therefore repairing projects must be carried out with recycled slate (which may not last as long since they may already be around 100 years old) or imported slate from England, Wales, Spain, or even further away.
Although the carbon footprint of different roofing materials has already been quantified, the environmental costs of importing slate has not yet been researched in detail, yet it is of increasing importance to Scotland since there are no local slate quarries left and our traditional buildings continue to get older.
Natural slate has a much longer lifespan than that of modern roofing materials. This piece of work will look at the carbon saved over the lifetime of the building from taking into account the processing and transportation of the material and seek to quantify how much carbon could potentially be saved by utilising local natural slate.
It is hoped that this work will help facilitate a move towards a more circular economy in the construction sector in regards to roofing materials and help in highlighting the benefits of Historic Environment Scotland’s work in trying to establish a new Scottish slate industry.
The climate emergency has made the industry more aware of where things come from and how they are made. There is an economic, environmental, and ethical argument to using locally sourced natural stone as a roofing material, however this has never been quantified in terms of the potential carbon saved.
The construction sector is focused on initial costs as opposed to durability and often cheaper, less durable materials that are cheaper to build are utilised in favour of more robust materials that would long outlast modern construction materials.
By researching the environmental benefits of using slate as a roofing material it is hoped this information can be used so that slate might be chosen at the design stage and help construction projects meet environmental requirements.
Glasgow Caledonian University, Historic Environment Scotland, BE-ST