Geomembranes can range in thickness depending on their use-case; however, 60 mils is the industry standard, and most commonly found dimension. An average range lays anywhere between 20 and 60 mils. Thicker does not always mean stronger when it comes to geomembranes. Reinforced scrims and highly advanced materials can provide similar if not higher levels of durability and flexibility.
The thicker a geomembrane is, the heavier and harder it will be to install. Some of the heaviest membranes require professional machinery to transport and properly handle the material. Others can be as thin as your standard grocery bag, like in the case of PVC.