Types of Slate
The geology of slate is important, as it affects the appearance and longevity of the finished roof. Often the word “slate” has been used to describe mudstone, limestone and other types of roofing stone. However, their properties are significantly different, requiring a different method of use.
The most common, and strongest, type of slate comes from metamorphic rock, which has been exposed to immense heat and pressure over millions of years. This gives good slate some useful properties:
- It can be split thinly, reducing the weight of the roof.
- Low water absorption: reducing the risk of frost damage, permitting an extremely long service life and excellent durability
- Hardness: reducing the mass of material required. Compared with natural slates, concrete or clay tiles are substantially thicker. A flawless slate has a distinctive ring when struck.
- Workability: Slate can be cut, holed and trimmed using hand tools, making for fast, safe work when completing the roof.