When most construction professionals think of a ‘waterstop,’ they generally refer to a dumbbell or ribbed profile extrusion of thermoplastic or rubber material, 102 to 305 mm (4 to 12 inch.) wide, installed in a concrete joint.The most widely used waterstop is polyvinyl chloride (PVC). Strong and flexible, these products have been used due to ease of welding and inherent resistance to groundwater and common waste water treatment chemicals. There are now myriad metal, plastic, asphaltic, and hydrophilic materials, with differing compositions and profiles, utilized to stop water ingress through joints in concrete structures.

A waterstop is a material embedded in the concrete, with the singular purpose to obstruct the passage of water through the joint. In other words, it is not an elastomeric sealant adhered to the exposed surface of a joint. Beyond the joint, waterstops cannot prevent migration of water vapor or capillary moisture potential through a concrete slab to protect the flooring system from adhesion failure or deterioration.