Can Chinese Roofing Slate Meet Standard of EN 12326 S1?

Chinese Roofing Slate
Quarry & Factory

EN 12326 S1 Standard Explanation

The EN 12326 standard defines the quality and performance requirements for natural slates and similar materials used for roofing and external cladding. The S1 rating specifically addresses the slate's resistance to freeze-thaw cycles. Here’s a breakdown:

S1 Freeze-Thaw Resistance Criteria

  • Testing Method:
    The slate undergoes 56 freeze-thaw cycles in a laboratory, simulating the real-world conditions where water freezes and thaws repeatedly.

  • Pass Criteria:

    1. After testing, the slate’s flexural strength (bending strength) must not decrease by more than 20%.
    2. The slate must show no visible damage, such as flaking, cracking, or delamination.

S1, S2, and S3 Classifications

  • S1: The slate remains stable after freeze-thaw cycles, making it suitable for use in severe climates with frequent freeze-thaw conditions. This is the highest quality level.
  • S2: The slate shows moderate performance degradation and is suitable for milder climates.
  • S3: The slate has poor freeze-thaw resistance and is generally unsuitable for external applications.

Why Chinese Roofing Slate Do Not Meet S1 Standards

  1. High Calcium Carbonate Content:
    Many Chinese slates contain a significant amount of calcium carbonate, which makes them more porous and prone to water absorption. When water freezes and expands, it causes structural damage, making it difficult to pass the S1 standard.

  2. High Porosity:
    Increased porosity allows water to penetrate the slate more easily, making it vulnerable to freeze-thaw damage.

Importance of S1 Rating

For roofing and cladding materials exposed to harsh climates (e.g., in the UK or Northern Europe), choosing S1-rated slates is essential to ensure durability, weather resistance, and safety.

As one of the earliest exporters of roofing slate in China, Westone's parent company began exporting roofing slate to the UK over 25 years ago. However, we must clarify that China no longer produces roofing slate that meets the EN 12326 A1 T1 S1 standards. This is primarily due to the high calcium carbonate content in Chinese slate, which makes it unable to pass the S1 frost resistance test.

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