Internationally Accepted Standards for Roofing Slate
Not all slate is the same. Independent testing of slate reveals its ability to protect and enhance the aesthetic appeal of a building over time. Independent testing is key in determining the overall cost of ownership and the value a slate roof can add to a property.
In 1957, a national standard for roofing slate was developed by the American Society for Testing and Materials (ASTM). ASTM Standard C406 addresses the material characteristics, physical requirements, and sampling procedures appropriate for the selection of roofing slate. More recently the organization has become international in scope.
Within the C406 Standards are three grades based on the physical properties of the slate, including strength, water absorption and weather resistance.
ASTM C406 and Slate Grades
The ASTM C406 standard three grades for classifying roofing slate are: S1, S2 and S3. Slate grades are intended as a prediction of the slates expected service life:
- 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.
All Greenstone Slate is Graded S1
Greenstone Slate® has been tested by National Slate Association approved facilities and meets the ASTM C406 Grade S1 slate standard. Our slate has all the physical characteristics of the best quality slate available anywhere in the world. Read the Greenstone Slate 100 Year Warranty statement to learn more about how we stand behind the material and the manufacturing of our slate.
We are ready to assist you with selecting and specifying slate, advising on slate roof or cladding installation, or to help a homeowners find a contractor. Simply call 800-619-4333 or contact us here.
Technical Resources
Learn more about engineering standards and the quality of Greenstone Vermont roofing slate.