Many natural stone products are 18mm thickness for outdoor use and exterior porcelain paving is usually around 20mm in comparison to concrete paving slabs which are often in excess of 35mm. Does this mean the concrete option is stronger and more resilient? The simple answer is no.

Natural stone and porcelain paving have high flexural and compressive strength values (bending strength and ability to withstand pressure from above), meaning that even when constructed at a thinner depth, they are actually rated stronger than concrete at a thicker depth. In fact at 20mm thickness, porcelain paving can even be used on pedestal risers that suspend the paving between 'legs' so it can be used on flat rooves and balconies whereas concrete has to be a minimum of 50mm to be used in this way. With natural stone, this should always be laid on a full mortar bed. 

In summary, the thickness of the paving is not the important factor when determining the strength of paving as it is the test data that matters and shows the true resilience of the material.