Thickness is one of the basic index properties used to control and track the quality of many geomembranes. Additionally, many mechanical properties (for example, tensile yield strength, puncture strength, etc.) can be related to core thickness. Core thickness values may also be required in calculation of some parameters such as diffusion coefficients or tensile stresses.

The measured core thickness of geomembranes may vary considerably depending on the pressure applied to the specimen during measurement. To reduce variation in measurements and the chance of unrealistically low values due to excessively high pressures, a specific gage point geometry and applied force are prescribed in this test method.

The test method is applicable to all commonly available textured geomembranes that are deployed as manufactured geomembrane sheets.