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Slate
Slate is a prestigious roofing material, which combines aesthetics and durability. Dimos offers the widest range of tools and fastening systems on the market for working with natural slate and fibre cement.
Natural slate, a noble roofing material
Natural slate is a metamorphic rock similar to schist.
Slate has been used for roofing since the Middle Ages in many parts of Europe, especially in France, notably in the West and the Ardennes region: it was historically used in regions with or near quarries, before being widely exported. Slate roofs can be found throughout northern Europe.
In the late 20th and early 21st century, most of the historic slate basins successively closed upon becoming depleted. Today, the vast majority of slate used in roofing comes from recent quarrying operations in Spain, Canada, China and Brazil.
When it comes to roofing, slate is synonymous with durability: it is not uncommon for a slate roof to last for up to a century. It is the signature material for covering historic buildings. Slate tiles come in a wide variety of shapes, thicknesses and colours, giving roof slaters free rein to their creativity.
Synthetic slate, a major improvement through years
Synthetic slates, or fibre-cement slates, are roof elements resembling natural slate, but which are actually moulded in a factory from cement and mineral fibres. The use of asbestos in their composition has earned them a bad reputation, but the use of asbestos has actually been banned since 1997, which means that synthetic slates are now safe.
Fibre-cement slates have evolved considerably over the years: they are now treated with an anti-moss coating on the outside and a pore filler on the inside. Although their durability is still less than that of natural slate, they have truly become a technical product offering good resistance to the elements provided they receive regular maintenance.
Their increased durability coupled with their lower purchase and installation cost make them an interesting alternative to natural slate.
Laying methods
Laying a slate roof is a technical job that must comply with location-specific regulations. These are influenced by architectural tradition, distance from the coast, and weather conditions, wind, snow, etc.). Main roof laying methods initially developed around major slate basins. We therefore find methods such as the Angevine (from Anjou, France), the Schuppen (Germany), the Ligurian (Italy) and many other region-specific laying methods.
We generally distinguish between the tiling of the ‘square plan’, i.e. the entire flat slope (excluding any roof components and without any changes of roof shape), and the tiling of more complex parts: ridges, hips, valleys, or other more decorative architectural structures (e.g. turrets and twisted steeples, or patterns).
Laying a slate roof
A slate roof is installed on the sides of the roof after the framing has been prepared. To ensure the roof is waterproof, it is important to observe the minimum height so as to prevent the rise of water through capillary action between two overlapping roof elements. This is why there are many differently sized slate formats available (e.g. 33×22, 40×40) depending on the slope, region and rainfall. To ensure the building is waterproof, it is therefore essential to calculate both the surface to be covered, and the batten gauge (i.e. the visible part of a tile that is directly in contact with the elements).
Fastening methods and fixings vary depending on the region, the type of building and finish, and the quality of the slate: they come with a clip or nail end, and can be mounted on, or driven in. It is important that the tiler should set out the roof prior to fixing. Rafters and tile battens are then added to the framing taking account of the fixing method and gauge. Slate hooks and nails come in a variety of metals (e.g. stainless steel of different grades, copper) depending on the region and budget.
The tiler then marks out the gauge and the appropriate length of tile course before laying the slates. When designing the roof, it is important to install ventilation outlets and closure strips, which are essential for ensuring the durability of the roof. These elements may be made of zinc or plastic. Today, the trend is towards products and installation techniques that conceal the zinc work and fastening elements.
Slater tools
The job of a slater involves cutting the slate into the right shape and fixing it to the battens.
A slater’s hammer and anvil are designed to make this cut in a shearing movement: they are the most emblematic of all tiling tools, and actually offer the best results.
Other tools, such as slate cutters or pliers, are useful for series production, or offer greater usability for less experienced roofers.
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