Created on 04.22
A Complete Guide to BS EN 12326 Slate: What A1-W1-T1-S1 Means for Your Slate Roof (2026 Edition)
Choosing natural stone for a roof can feel complex. If you work with Natural roofing slate for the UK or European market, you may see the code A1-W1-T1-S1.
These codes are not random. They show how slate performs in key tests under EN 12326-1.
This guide explains the standard using real test data from our Model 681 slate sample.
What is BS EN 12326?
BS EN 12326-1 is the European standard for slate used in roofing and external cladding. It helps buyers and specifiers judge slate by performance, not just by appearance.
Natural stone can vary from quarry to quarry. This standard gives everyone a common way to compare products.
It is important to know that this standard does not promise a fixed roof life. How long a roof lasts also depends on design, installation, weather, and care.
What A1-W1-T1-S1 Means
Our Model 681 slate sample was tested by SGS under report No. XMIN2501000084CM01EN. The sample was classified as W1, A1, T1, and S1. Here is what each code means.
- A1 – Reaction to Fire: A1 means the slate is classified as non-combustible for reaction-to-fire purposes. In the report, the sample was deemed to satisfy the A1 requirement without further testing. This is important for building safety. It shows the tested slate meets a high fire classification under the standard.
- W1 – Water Absorption: W1 is the water absorption class. In the SGS report, the Model 681 sample had a mean water absorption value of 0.05. Low water absorption is good. It helps reduce damage from freeze-thaw cycles and supports long-term roof performance in wet climates.
- T1 – Thermal Cycle Test: T1 relates to how the slate handles heating and cooling. The report said there were no changes in appearance, no surface oxidation of metallic minerals, and no colour changes after the test. This suggests the slate has good visual stability. It is less likely to change color or develop surface problems over time.
- S1 – Sulfur Dioxide Exposure: S1 shows how the slate performs in sulfur dioxide exposure tests. In the report, the sample had an apparent calcium carbonate content of 2.50 and showed no colour changes in Solution A. This means the tested sample performed well in the S1 test. Again, this result applies to the tested sample and the test conditions in the report.
Why RTS is a Reliable Slate Supplier
For architects, distributors, and contractors, stable quality matters. Red Tree Slate (RTS) is a Direct quarry slate supplier in Shaanxi Province, which helps keep product properties more consistent.
Our Model 681 slate is a sericite slate with a microscale crystalloblastic texture. The SGS report showed a characteristic modulus of rupture of 25.0 N/mm² in transverse orientation and 23.6 N/mm² in longitudinal orientation.
We also supply standard roofing slate sizes such as 200 mm x 200 mm x 5 mm. The report shows the tested dimensions stayed within the declared tolerance range.
For international projects, a tested slate with steady physical performance can make planning easier and reduce risk on site. RTS offers a Wholesale roofing slate China supply model for commercial projects.
FAQ: Sourcing from a Chinese Slate Quarry
- Is Chinese slate suitable for UK and European projects? Yes, if it has been tested to EN 12326-1. The Model 681 sample in our report was classified as W1, A1, T1, and S1.
- Can I get a quote for large projects? Yes. We support bulk roofing slate supply for commercial and residential projects. As a quarry-direct source, we can quote by size, thickness, quantity, and destination. Our Factory-direct slate tiles model helps simplify buying.
- Do you keep stock for export orders? We keep production and supply capacity for export orders. Lead times depend on the required size and quantity. Please contact us with your project needs.
Notes on Test Data
- The data in this article comes from SGS test report No. XMIN2501000084CM01EN for the Model 681 sample. The results apply only to the tested sample.
- For project use, always check that the tested sample matches the material you plan to supply.