Quality & STANDARDS COMPLIANCE
All slates are produced under strict quality control. Our clients put them into test referring to BS EN 12326 and ASTM C 406, they are compliant with requirements in standards and A1-S1-T1 rated. 75 years will be expected to last for roofing.
DOWNLOAD TEST REPORTS
BS EN 12326-1:2004
BS EN 12326-1:2004 is the new European standard for slate and stone products for discontinues roofing or cladding. This replaces the old BS 680-2:1971.
Following is a brief explanation, explaining the tests and standards our slate reaches in order to conform to the new standard.
Tolerances are provided for the length, width, individual thickness, flatness, rectangularity and edge deviation, of the slate being tested.
The packed thickness for 100 slates must be calculated for every pallet to allow for the calculation of the average roofing slate thickness, with a reduction applied on the surface finish.
2. Flexural Strength
The slate test samples are supported on two bars and a third central bar is pushed down on the slate until failure occurs. The test is carried out both parallel and perpendicular to the long edge of the roofing slate. From the results gained a characteristic modulus of rupture is calculated (basically a ratio) and the larger of the two values is used for calculating the minimum individual thickness of the roofing slate.
3. Water Absorption
The slate is dried to a constant weight; it is then immersed in water. The absorption percentage is determined via the difference in mass. If the value obtained is less than 0.6%, the slate is classed as A1, whereas, if it is above 0.6% it is classed A2.
4. Freeze-Thaw Test
This test is only required on A2 classed slates. The slate is submitted to 100 cycles of freezing in air, followed by thawing in water, once this is complete the flexural strength test is repeated. If there is a significant change in results, the slate is deemed not suitable and does not pass the European standard.
This test verifies the amount of graphite present in the slate, as well as oils and other organic matter. If the slate contains in excess of 2% graphite, it fails the test and does not pass the European standard.
These groups determine the thickness of the slate. The groups also determine the method of sulphur dioxide testing,
Sulphur Dioxide Exposure For Slate With Less Than 20% Carbonate
The slate is exposed to sulphur dioxide at two different concentrations for a duration of 21 days. Depending upon changes during the test, one of 3 codes will be given. The code is then used to apply a thickness adjustment, depending on the carbonate content of the slate.
Sulphur Dioxide Exposure For Slates With More Than 20% Carbonate
The slate is subjected to surface scraping before and after exposure to sulphur dioxide vapor. After each exposure there is an increase in material removed, this carries on until the depth of softening is reached. A thickness adjustment is then applied to all slates, except for in the case where the softened layer is greater than 0.7mm.
Thermal Cycle Test
The slate is subjected to 20 cycles of immersion in water immediately followed by drying at 100 degrees Celsius, upon completion an inspection occurs for the presence of potentially harmful mineral components:
• T1- for slate with colour changes that do not affect the structure and form runs of discoloration.
• T2- for slates with colour runs that do not cause structural change.
• T3- for slates where holes may be formed from the oxidization of inclusion.
If exfoliation, splitting or other structural changes occur, the roofing slate does not pass the test and is therefore not up to European standard.
Geological appraisal that includes optical microscopy, x-ray diffraction and scanning electron microscopy. This examination determines the type of roofing slate and weather there is any presence of harmful or dangerous structures or minerals.
-C119: Terminology Relating to Dimension Stone
-C120/C120M: Test Methods of Flexure Testing of Slate (Breaking Load, Modulus of Rupture, Modulus of Elasticity)
-C121/C121M: Test Method for Water Absorption of Slate
-C217/C217M: Test Method for Weather Resistance of Slate
The American Society for Testing and Materials (ASTM), is a free acting society, with the goal of keeping a high national standard for materials. The ASTM standards for slate are somewhat regulated by members of the National Slate Association (NSA) with members from leading American quarries.
This is a compleatly voluntary standard. Manufactures are able to send their products to ASTM labroratories across the country, thus making sure their products meet ASTM standards.
Roofing Slate ASTM Requirments (C406) can be read out here
Simply put, ASTM tests slate in three categories.
1) Breaking Load.
2) Water Absorption.
3) Depth of Softening.
Based on these three tests, Slate is put into 3 categories.
A. ASTM C 406 Grade S1: Expected service life in excess of 75 years.
B. ASTM C 406 Grade S2: Expected service life 40-75 years.
C. ASTM C 406 Grade S3: Expected service life 20-40 years.
Test Procedures as follows:
1. Water Absorption of Slate
Testing was performed per ASTM C 121-06, Standard Test Method for Water Absorption of Slate. The samples were dried in a ventilated oven at 60℃ for 48 hours. At the 46th, 47th and 48th hour, the sample were weighed to ensure that the weight was constant. The samples were then completely immersed in distilled water at 20℃ for 48 hours. The samples were removed one at a time, wiping the surface dry with a slightly damp absorbent towel, and immediately weighed.
2. Weather Resistance of Slate
Testing was performed per ASTM C 217-94(2004), Standard Test Method for Weather Resistance of Slate. The samples were dried in a ventilated oven at 60℃ for 48 hours. At the 46th, 47th and 48th hour, the sample were weighed to ensure that the weight was constant. The samples were marked and measured for thickness using a micrometer. Using a hand scraping tool, the samples were scraped at a 30° angle with 3 lbf of applied pressure on the cutting edge. The specimens were again measured for thickness and recorded as the "depth of softening prior to the acid treatment". The scraped samples were soaked in a 1% sulfuric acid solution for 7 days at ambient temperature. After the 7th day, the samples were measured and scraped again using the above procedure. The thickness measurements were recorded as "depth of softening after the acid treatment".
3. Modulus of Rupture
Testing was performed per ASTM C 120-06, Standard Test Methods for Flexure Testing of Slate (Breaking Load, Modulus of Rupture, Modulus of Elasticity). The samples were dried in a ventilated oven at 60℃ for 48 hours. At the 46th, 47th and 48th hour, the sample were weighed to ensure that the weight was constant. The center of the specimens were located and marked and then span lines were marked parallel to, and 1 inch from the center line. The specimens were placed flat on knife-edges of a testing fixture, and a constant load was applied at a test speed of 0.05 in/min until failure.