Composite GCL’s are constructed by either adding a thin membrane to a standard GCL or by adhering sodium bentonite directly onto a geomembrane. The thin membrane that is applied onto a standard GCL is designed to act as a vapor barrier or to protect the bentonite from harmful contaminants. When the bentonite is applied to a geomembrane, it acts as a composite lining system. The geomembrane backing can either be smooth or texted and can be welded together.

The most commonly used type of GCL is made by encapsulating sodium bentonite between two layers of geotextiles. There are several varieties of products manufactured to accommodate different needs for internal shear strength, friction angle and permeability. One of the main concerns with a GCL is to insure that the material being contained is compatible with the sodium bentonite.