Waterproofing: An Important Part of Concrete

man applying sealant

Waterproofing is important in any structure. Once water seeps through the concrete, the foundations can be undermined and its reinforcement vulnerable to rusting.

Waterproofing can include sealants painted on the surface of concrete, admixtures that reduce permeability of the concrete mix, and waterstops. Waterstops are materials installed in concrete structures at concrete joints ‒ construction, expansion and contraction ‒ to prevent water from seeping through. A variety of materials are used for waterproofing. Although a small component of the whole construction process, choosing the right type is important, especially in structural components.

Materials used for concrete water stops and sealants


Polyvinyl chloride or PVC waterstops are the most common type used for concrete joints because they can be installed in wet or dry conditions, come in a range of sizes to suit nearly all types of construction joint, and are extremely durable. However, challenges may arise with installation during the concrete pour.


Bentonite is a clay compound that swells or expands up to 16 times once it comes into contact with water. It functions like a sponge and is often used to provide support in excavations during a concrete pour. Because of its characteristics, bentonite is often used to fill small cracks and voids in the concrete and can be left in excavations, to form a water sealant. But, because of its swelling properties, it is important to keep the bentonite dry before pouring the concrete. Additionally, in its powder form, bentonite can be included as an admixture in a concrete mix to provide waterproofing properties.


Like bentonite, urethane swells to about 350 per cent of its original volume once it is in contact with water. It performs the same function as bentonite; however, urethane’s properties are prone to eventually wear out after too much exposure to water. Both materials are known as hydrophilic compounds due to their reaction with water.


Although it is installed like PVC, metallic waterstops are mostly used in huge construction projects like dams or where the concrete will be exposed to extreme conditions and temperature.

Water is a problem in many concrete and brick structures. Make sure you select the right method to manage water penetration and use the right material.