Waterproofing for Retaining Wall and Roof Garden

Waterproofing for Retaining Wall and Roof Garden

The infiltration of water through the cold joints of a retaining wall can cause the reinforcing steel in the wall to rust and, over time, damage the integrity of the wall. Also, concrete has a tendency to absorb moisture through capillary action. As a result, moisture can travel through most concrete walls. The right type of waterproofing membrane can help alleviate this problem.

The visible signs of moisture in a concrete retaining wall are spalling or scaling of the concrete. If the downhill space beyond the retaining wall is used as living space, water infiltration can cause unsatisfactory conditions, which are very expensive to correct.

Historically, builders have applied hot tar reinforced by mesh behind concrete or masonry walls to seal the cement. While this mechanism has proven to be effective, over time, it tends to fail since tar will eventually deteriorate and crack.

Today, the advancement of technology has reached a point where numerous fail-safe systems have been developed. Accordingly, the failure of retaining wall waterproofing is no longer accepted by the construction industry. To render a concrete wall waterproof, two technologies can be used: “sheet waterproofing membranes” and “liquid applied membranes.”

Sheet waterproofing membranes

Sheet waterproofing membranes are produced by several manufacturers for different applications and conditions. The primary characteristic of all sheet waterproofing membranes is flexibility. These membranes are designed to stretch to a certain degree.

Some membranes are self-adhering and usually available in rolls. To apply the membrane, a protection film is peeled off, and the membrane is adhered to the back of the concrete wall, in sections, until it covers the entire wall.

Other membranes are composed of 15 or 20 mils of High Density Polyethylene sheets that are laminated with granular Bentonite. Bentonite is a form of clay with expansive properties in the presence of water. This product is draped against the back of the concrete wall with the granular Bentonite side against the wall.

Bentonite membrane sheets are lapped until all of the exposed concrete is covered. All joints are taped and sealed. The sheets are connected to the wall at the top by an aluminum termination bar nailed to the wall. Once installed, if water travels to the membrane and comes in contact with the Bentonite, the Bentonite will expand and stop the infiltration of the water any further behind the membrane.

There are other types of sheet waterproofing membranes, and they are installed in the same fashion as Bentonite sheets.

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 back fill.

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

About SteelCore Builders

As a division of Trush Construction Company, the SteelCore Builders crew and management have been doing structural concrete and strengthening since 1987. Due to our firm’s extensive engineering expertise and exceptional reputation, we are often retained to undertake very difficult and complex projects. Our continuous research and testing of new building materials and technologies enable us to address unique situations that other firms cannot.