David Cooke from Cupa Pizarras discusses the versatility of natural slate when it comes to aesthetics, and the resulting design freedom it offers architects, giving recent examples
In an age where the environmental impact of our actions is rightly under scrutiny, natural slate represents a highly sustainable roofing or cladding choice. A 100% natural material, its production process from quarry to installation is a highly efficient one that does not require any chemical treatment. Independent studies, such as the Inventory of Carbon and Energy (ICE) at the University of Bath, have highlighted that natural slate has the ability to offer the lowest environmental impact when compared to alternative roofing materials.
Performance & aesthetics
With a lifespan of up to 150 years and needing only minimal maintenance, natural slate also provides a high performance and practical roofing option. In the material’s early use, it was favoured for the construction of castles and churches due to its weather resistance. However, in more modern times, it has become a popular choice for its non-combustibility and sustainability credentials. Natural slate can create a sleek and uniform aesthetic and has the added benefit of being resistant to unsightly fungus or mould growth. Also, with the growing trend for unique pitched roofs that incorporate complex shapes, natural slate can play a key role in a project’s success. The material can be easily cut into a wide range of sizes, for example larger, 50 x 30 cm and 60 x 30 cm formats, and shapes including rhomboid and half moon to complement a wide variety of architectural designs.
The versatility of natural slate also means that it can be used as a contemporary cladding material. An example of this can be seen at a recent project in Peckham, south London, where a 72º upper mansard was created to provide a truly striking aesthetic. Mansards are becoming an increasingly popular choice due to the way in which they efficiently use interior space, as well as how they allow natural slate to be combined with other materials. In the case of Costa Street in Peckham, natural slate was selected due to its light weight and superior strength to weight ratio, enabling a dramatic ‘leaning’ effect to be achieved.
For a £2m development at the Colin Forbes Building – part of the Sedgwick Museum of Earth Sciences at the University of Cambridge – slate cladding was used alongside brickwork to provide a contemporary look, and complement the existing building. A ‘random’ natural slate rainscreen cladding system was specified in a range of dimensions to create a varied and dynamic finish. It also allowed the impression of stratified rock to provide a further visual cue to the geological nature of the work conducted inside.
A traditional approach
While cladding provides a striking modern use for natural slate, the material remains a popular choice for more traditional building designs and heritage roofs too. In particular, many projects can benefit from the longstanding design choice of laying natural slate in ‘diminishing’ courses. This approach, sometimes referred to as random slating, was originally the result of many Scottish quarries historically producing slates in varying dimensions and thicknesses to maximise the quarry output. This led to the practice of laying the slates with the largest ones at the base of the roof and the smaller ones near the ridge.
Some manufacturers offer options in a random format should the distinctive aesthetic be required. This was the case during a recent renovation of the historic Marine Hotel in Troon, Ayrshir located on the edge of Royal Troon Golf Course. The choice of product closely replicated the colour and thickness of the original slates while maintaining the diminishing courses used on the original roof.
Finally, natural slate can be used to complement other natural materials, textures and colour schemes to create unique architectural designs, as evidenced by a recent new build development in Whitstable. Pitched roofs feature extensive use of dark grey aluminium glazing systems, including rooftop lanterns and large sloping roof windows. The design also included high quality natural timber cladding, sedum green roofing and natural stone blockwork, used alongside natural slate. achieving the desired look and a durable result.
While natural slate has a long and established history as a building material, the design possibilities, sustainable credentials and performance benefits for modern construction projects are clear. Manufacturers offer product portfolios of natural solutions which can provide the ideal result for specifiers, whether it is a unique and contemporary project or one looking to maintain traditional aesthetics.
David Cooke is business development manager at Cupa Pizarras