NATURAL SLATE - THE ULTIMATE SELF-BUILD MATERIAL?
26 June 2015
Few building materials are as capable of being used in a multitude of self-build applications as natural slate.
Externally, the material can be used for roofing, sills and copings, cladding, paving, walling and landscaping. Internally, it can be used as wall and floor tiles, worktops, fire surrounds and hearths, even house signs and tableware.
It is the natural density of Welsh slate, achieved over 500 million years, which makes it such a versatile material, and so eminently suitable for the self-builder who will have chosen this route to achieve a home they might not have been able to otherwise in terms of quality, design, innovation and the environment. Welsh slate in all its finishes and colours helps them achieve all those objectives.
Widely regarded as the finest natural slate in the world due to its density, Welsh Slate benefits from a number of highly practical properties that make it an exceptional building material. It is the most durable slate in the world, with a productive (and guaranteed) life of 100 years. It is waterproof and unaffected by normal extremes of temperature, highly resistant to acids, alkalis and other chemicals, and it is colour-fast and non-fading, even in UV light.
Welsh Slate roofing is commonly removed from roofs after 100 years not because they have failed but because the roof timbers holding them up have failed. The slates may then be re-used. Penrhyn Heather Blue slate, for example, was removed from St Asaph Cathedral after 400 years in use and reused.
Natural slate’s properties allow complex and intricate roofs to be designed but for the most flexibility in terms of design details, choice of sizes and economy, pitches should be kept at 30˚ or above.
Self-builders considering complementing natural slate’s recyclability with solar panels should be aware that bespoke fixing kits for slate roofs are readily available. However, as with all roofing materials, natural or man-made, where access of work is required over them, loads should be evenly distributed with crawling boards, and if necessary, padding used to minimise breakages.
Natural slate’s density also comes into play as a cladding material, allowing it to be used for panels as thin as 20mm. A design choice currently popular is the use of relatively large slate panels in a natural riven or sleek contemporary fine rubbed finish. These are fixed in metal grids appropriate to the size and thickness of the panels and secured to an external wall.
The material’s weathering and UV-resistant properties also lend themselves to walling, either as an aesthetic cladding to a structural wall or as a fully-performing structural wall in itself. If due to the vagaries of the British weather, mortar washes down and stains the slate, it can be cleaned with brick cleaners and other strong chemicals without affecting its colour or durability.
Welsh Slate’s natural beauty and performance characteristics also lend themselves to another contemporary trend, that of designs that run seamlessly from exterior to interior.
Welsh Slate has been used as floor tiles in homes for hundreds of years. The material is highly durable, colour-fast and with its high compressive and flexural strength make it an extremely strong flooring material which is easily maintained.
Misperceived as a cold material, its density actually enables it to retain heat (and cold) extremely efficiency (one reason why it is also used for tableware) and when used in conjunction with an under-floor heating system, it provides an extremely efficient means of managing temperatures within a home through all seasons.
And because it is chemically inert, non-combustible and unaffected by heat, Welsh Slate is a natural choice for kitchen and bathroom worktops. Its impermeability means it does not have to be sealed to ensure it doesn’t not stain or allow tastes or smells to be retained, only if a more glossy finish is required.
