The grass mat standard

Technically, yes, there are two types of test conditions – concrete base and field base tests.

The grass mat standard stipulates that all laboratory tests shall be carried out on a flat, rigid concrete. These are known as concrete base tests. (Alternatively they can be tested on a substrate of sufficient mass, density and thickness that makes no significant contribution to the test result.)

Products installed in combination with natural materials intended to influence their performance (e.g. soil) cannot be meaningfully tested in the laboratory. These tests – known as grass base tests – cannot be used to indicate the performance of the product under other conditions or in other locations. For example, if surfacing is installed and tested on a clay-based soil, it is almost certain that a greater critical fall height will be achieved under tests when the base is wet as opposed to when the base has been subject to a dry period.

When a supplier quotes a certification for a specific fall height that sounds too good to be true, they may have done a grass base test. You should always check with your supplier, and ask for proof of certification for concrete tests, as these will give the most accurate results.

Always remember to ask your supplier to clarify exactly what ground conditions their product has been tested on. For example, if the test states the mat was tested with a 140mm soil layer and mesh on a grass base, you will need to replicate these conditions on site in order for the grass mats to comply to their certification.