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Waterproofing Membranes

Concrete structures are not impermeable, especially if the cement was poured in stages and the entire structure is not monolithic. The joints between sections are called cold joints and water can travel through them. Also, concrete is a porous material and can absorb water through capillary action. To stop the water infiltration, a waterproofing membrane is used.

The membrane is typically applied to the exterior of the concrete foundation and wall where it comes in contact with water. Today, these membranes are very sophisticated and designed to permanently seal the concrete, provided that they are applied correctly and according to the manufacturer’s directions. We can categorize the modern membranes into two types.

Sheet Membranes

These membranes are manufactured and applied in a sheet form. Some have adhesive and are self-adhering. Others are intended to be draped on the back of the masonry walls and attached to the wall with a nailed termination bar fastened to the top of the wall. An example is sheets of 12 or 20 mil of High Density Polyethylene that are laminated with granular bentonite. Bentonite is a form of clay with expansive properties that expands in the presence of water. Once placed on the back of a concrete retaining wall if it gets wet the Bentonite will expand and stop the flow of water. An excellent characteristic of these membranes is elasticity of the material.

Liquid Applied Membranes

Numerous forms of liquid or fluid applied membranes have been developed by several manufacturers to address different conditions. The most common liquid applied membranes are Polyurethane-based. Others are Epoxy-based. Some Polyurethane membranes contain accelerators to aid in curing. Liquid applied membranes are typically installed with notched trawls, rollers or a heavy brush.

Other membranes are composed of cement-based materials, but they do not really form a membrane and don’t have an elastic ability. They are not desirable for waterproofing retaining walls. All membranes should always be protected by a Protection Board before placement of perforated pipes and drain rock for drainage.

If you would like to learn more about waterproofing membranes for retaining walls, please contact SteelCore Builders.