ASTM C406/C406M-22

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Designation: C406/C406M − 15 C406/C406M − 22
Standard Specification for
Roofing Slate
This standard is issued under the fixed designation C406/C406M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
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.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C119 Terminology Relating to Dimension Stone
C120/C120M Test Methods for Flexure Testing of Structural and Roofing Slate
C121/C121M Test Method for Water Absorption of Slate
C217/C217M Test Methods for Weather Resistance of Slate
3. Terminology
3.1 Definitions—Definitions shall be in accordance with Terminology C119.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 service life—a period of time over which the slate material is expected to require no repair or replacement due to weathering.
3.2.2 ribbons—narrow bands of carbonaceous material, darker in color than the surrounding slate. These ribbons are inclusions
of the original beds and are softer and less durable than the surrounding material.
This specification is under the jurisdiction of ASTM Committee C18 on Dimension Stone and is the direct responsibility of Subcommittee C18.03 on Material
Specifications.
Current edition approved April 1, 2015Aug. 1, 2022. Published May 2015September 2022. Originally approved in 1957 as C406 – 57 T. Last previous edition approved
in 20102015 as C406 – 10.C406/C406M – 15. DOI: 10.1520/C0406_C406M-15.10.1520/C0406_C406M-22.
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C406/C406M − 22
4. Classification
4.1 Roofing slate shall be classified by grade in accordance with the physical requirements of Table 1, with the classification
limited to the test specimen thickness, or greater thickness, as determined under Test Methods C120/C120M.
4.2 When comparing slates of the same grade and equal thickness, but from various sources, slates which meet the required
breaking load at the lowest specimen thickness will yield the best performance on the roof in terms of resistance to impact damage.
4.3 Expected service life of the various grades, depending on geographic location and environmental exposure, is as follows:
Grade Service Life (years)
Grade S over 75
Grade S 40 to 75
Grade S 20 to 40
5. Ordering Information
5.1 Color—The commercial color specified should be preceded by the words “unfading” or “semi-weathering” or “weathering”
to indicate the allowable change in the original slate color, over time, upon exposure on the roof.
5.2 Standard Roofs—Sloping roofs utilizing a nominal thickness of ⁄4 in. [6 mm], a
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