What does diminishing courses mean?
Yorkstone slates are traditionally random sized. The widths and lengths both vary. Slates are laid in diminishing courses from the larger ones at the bottom to the smallest at the top.
This method, although a little tricky to master provides a very pleasing result. The photograph alongside shows the subtle reduction in size as the courses ascend the roof, this is not generally noticed but you will probably appreciate the pleasant appearance and a sense of balance over the whole roof.
Yorkstone slates can range from over 1 metre (40") tall down to around 300mm (12") tall. The widths vary from as much as 800mm (32") down to the smaller slates of about 150mm (6") wide.
This traditional form of slating is very common in Scotland and the north of England. It does require the skill of an experienced slater but produces a weather resistant, high quality and most attractive roof.
Extremely durable 
