This specification covers the material characteristics, physical requirements, and sampling method appropriate to the selection of roofing slate for use as roof shingles. Slates not included in this specification are those containing soft carbonaceous ribbons. Roofing shall be classified either as Grade S₁, S₂, or S₃, wherein each grade shall meet specified breaking load, absorption, and depth of softening requirements.

1.1 This specification covers the material characteristics, physical requirements, and sampling appropriate to the selection of slate for use as roof shingles.

1.2 Slates not included in this specification are those containing soft carbonaceous ribbons. The wide variation in physical properties and composition of such ribbon slates render their service life uncertain under some conditions of use.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.