Slate is a beautiful, naturally occurring, organic material. As such, different kinds of slate may have widely differing chemical and mineral compositions.

These differences are determined by the geological characteristics of the quarry from which it was mined and may affect its long-term durability and stability.

There are some simple precautions you can take to ensure the slate you specify is of a high grade and comes from a reputable source:

Does the slate bear a CE mark? Some products on sale within the UK (notably a quantity of that from Brazil and China) do not. Without this qualification the product is not internationally classified as ‘slate' and might not be fit for purpose.

To read a summary of important independent research into slate from Brazil which is sold in the UK without having a CE mark click here.

Other national and international standards exist to help you specify slate roofing with confidence. Among these, slate that complies with BS EN 12326-2:200 or the more stringent NF Mark (French Norm) has attained a high level of quality and will give trouble free service.

Other notable international certifications include that of IQNET and its ISO 9001:2000. The AENOR and AFAQ classifications also embody international credence.

For more information on what the different standards mean, click on the relevant logo.