Slate

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Types and Durability

Description

Natural Slates

 Expected Lifespan

(Years)

 Adjustment Factors
Natural slate; size maximum of 610 x 335; to BS 680 Part 2 or ASTM C 406-00 with test certificate for specific batch delivered to site, including test for iron pyrites. 35+ 1st stage adjustment factor:

In industrial areas (heavy polluted): -15% years

In urban areas: -10% years

In suburban areas: -0% years

2nd stage adjustment factor:

Within 20m from express way: -20% years

Within 20m from major arterial road: -10% years

Within 20m from light traffic road: – 5% years

Test certificate from approved local testing authority : +15% years
Natural slate sizes up to 610 x 335. Slates comply with requirement of BS 680 Part 2 or ASTM C 406-00 with special reference to achieving water absoprtion, wetting and drying and the sulphuric acir immersion tests criteria 35
Natural slate of varyling orginal size and thickness and not complying with the requirements of BS 680 Part 2 or ASTM C 406-00 especially the water absorption, wetting and drying and/ or the sulphuric acid immersion test < 10 None

Combination of adjustment factor (1st stage and 2nd stage) should be added to obtain the durability values. Refer to durability calculator.

Assumption: Slates to be fixed in accordance with BS 5534 Part 1.

Natural slates fixing methods (by 2 nails or hook) are recommended by supplier

If aluminium or stainless steel or copper fixings are used, adjustment factors are provided for ferrous fixings:

  • Unprotected/ unplated ferrous fixings: -30% years
  • Galvanized or electroplated ferrous fixings: – 15% years

Note: The presence of iron sulphides in certain foreign slates has resulted in rapid splitting and deterioration. In the absence of proven local experience of slates from the source specified tests for the presence of such deposits should be made to the batch delivered.

Related standard :

Roofing slate is subjected to quality as a suitable roofing material, such as BS 5534 or ASTM C406 “Standard Specification for Roofing Slate” which references:

  • C120 “Methods of Flexure Testing of Slate”
  • C121 “Standard Test Method for Water Absorption of Slate”
  • C217 “Standard Test Method for Weather Resistance of Natural Slate”