Slates, whether natural or fiber based, allow the realization of perfectly waterproof covers, resistant to the wind. They are therefore widely used in oceanic regions. The laying on the hook on battens is now preferred to nailing on vault.
The roofing slates come from shale. These so-called "metamorphic" rocks are the result of tremendous tectonic pressures exerted on the clays during the geological ages. Slate schists are therefore rocks of sedimentary origin, which have the advantage of being easily sold in plates or "sheets" thin: slates. Depending on the original color of the clays, they may be different colors, ranging from black to orange or characteristic blue, preferred for the realization of roofs.
Slate is used in France for the production of blankets since the Middle Ages, following the architectural evolution of the houses, whose roofs became steeper. It then supplants, particularly in the regions of the west of France, stubble and terracotta.
It is experiencing a great development in Anjou and in the neighboring provinces, the region of Angers being for a long time the main area of extraction and transformation of slate schists. The depletion of the deposits and the cost of their extraction will shift sources of supply to Spain, Portugal and South America.
This name is usually referred to as synthetic slates, cement-based and fiber-based. Since 1997, they have not been containing asbestos. They are produced in the same thickness and format as natural slates, and are similar to these ones. They can be used for roofing or cladding.
The lack of stability of the hue in the long run is their main fault.
The different types of pose
For the laying of slates in a conventional way, work is done by shifting each row by half a width compared to the previous one (staggered joints).
Pose said "economic"
This way of doing things reduces the recovery, so the total number of slates, but is only applicable on slopes of at least 50%.
The square slates are placed with their diagonal in the direction of the slope, on battens separated by half of this diagonal, with overlapping sides of the slates.
It is necessary to choose rectangular slates of big model (400 x 240 at least). They are not posed contiguously on the same row, which therefore decreases the lateral overlap.
Developed skeleton laying, more economical than simple laying.
Cutting a slate
Cutting a slate requires specific tools:
- the roofer's hammer,
- the roofer's anvil.
A picket with the tip of the roofer's hammer on the cut line allows for a kind of dotted weakening slate.
The dotted line being positioned on the anvil, pressure is exerted on both sides of the slate to break it. The cutting line can be corrected with the hammer.
(photos / visuals: © DIY-Prod, except special mention)
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