SI (Compressive Strength ASTM C140-15). The is the amount of pressure per square inch that may be applied before the stone breaks

Absorption Rate (ASTM C140-15). A low absorption rate is crucial to prevent stone holding onto water, especially in colder climates where high water content can result in the stone cracking

Coefficient of Friction Rate (ASTM C140-15). This is the slip resistance rating o the stone to ensure if is safe for use outside

Furthermore, all products from Natural Paving are CE marked to ensure they meet with strict EU regulations that were introduced in 2013. European standards EN1341 (flagstones), EN1342 (pavers) and EN1343 (kerbs) specify the requirements and test methods for each of these. The CE testing covers areas similar to ASTM including water absorbency, flexural strength and frost resistance.

All natural stone products have been tested to show the various properties of each stone and how it is likely to react under different circumstances.