Grades Of Roofing Slate

Welsh slate still comes in 3 grades referred to as capital 5 5mm thick county 7 mm thick and celtic 9 mm thick.

Grades of roofing slate.

N is cupa s natural selection. Standard grade rough texture. A standard grade slate cupa h selection will be less uniform and will require more sorting prior to use. Greenstone slate is measured by eye to thickness and is then split by hand.

But the finished project will look as good if due care is taken of the slate grading. Roofing slates are rated through the american standards of testing and materials and given a slate classification from s 1 to s 3. According to astm test c 406 roofing slate falls into three grades of classifications. S 1 will provide a service life of over 75 years s 2 will provide a service life of 40 75 years.

Slate grades are intended as a prediction of the slates expected service life. Welsh slate being very flat and smooth as well as a nominal 5mm thickness. Grade s1 slate has an expected service life of more than 75 years. Grade s2 slate s service life is 40 to 75 years.

Grade s3 slate has an expected service life of only 20 to 40 years.