Why is waterproofing a retaining wall important?

Unchecked moisture can increase hydrostatic pressure, contribute to cracking and deterioration, and allow mold growth. A suitable waterproofing approach helps manage water, support structural performance, and protect adjacent spaces. Always evaluate site and wall conditions before selecting a system.

What are common waterproofing methods for retaining walls?

Common approaches include sheet membranes, fluid-applied membranes, cementitious coatings, bentonite systems, and integral admixtures—typically paired with appropriate drainage. The right choice depends on wall type, substrate condition, detailing, climate, and installer expertise.

When would I choose a sheet membrane vs. a liquid-applied membrane?

Sheet membranes provide consistent, factory-controlled thickness and clear lap detailing. Liquid-applied membranes form a seamless, monolithic barrier and can be helpful around penetrations and complex geometries. Selection often comes down to substrate, detailing requirements, budget, and installer training.

Do I still need drainage if I waterproof the wall?

Yes. Drainage components—such as prefabricated drainage composites, perforated pipes, or weeps—help relieve water and reduce hydrostatic pressure. Drainage is typically used alongside the membrane to support performance and help protect the waterproofing layer.

Can cementitious waterproofing be combined with other systems?

Often yes. Cementitious coatings can serve as part of a system—e.g., smoothing/parge or negative-side applications—alongside sheet or liquid membranes where appropriate. Confirm compatibility and follow manufacturer guidance and project specifications.

Which MEL-DRAIN model should I use?

Model selection depends on design and loading. As a general field guideline referenced in the article, lighter-duty options can be suitable below roughly 10 feet of soil cover, while heavier-duty options are considered beyond that. Verify with the project engineer and product data for flow capacity, compressive strength, and filter fabric type.

Waterproofing a Retaining Wall

A Guide from W. R. MEADOWS, INC.

retaining wall waterproofing

Retaining walls are an important aspect of any construction project that involves a significant change in elevation. They are designed to hold back soil or other materials, preventing erosion and protecting the foundation of a building or structure. They are commonly used to create level areas for building, and are crucial in managing the flow of water and preventing damage. However, retaining walls are also susceptible to water intrusion, which can lead to cracking, deterioration, and ultimately, failure.

To prevent water damage and ensure the longevity of your retaining wall, it’s crucial to incorporate waterproofing measures into your design. In this blog post, we’ll cover some of the best practices and products for waterproofing a retaining wall.

The Importance of Waterproofing Retaining Walls

Waterproofing retaining walls is crucial for several reasons:

Structural Integrity: Water can seep through the soil and infiltrate retaining walls, causing damage over time. Waterproofing helps maintain the wall’s structural integrity and ensures that it remains stable and functional.
Preventing Water Damage: Without proper waterproofing, water can seep through retaining walls, causing erosion, and potentially damaging nearby structures, such as homes or buildings. Waterproofing prevents this water damage and protects your property.
Mold and Mildew Prevention: Water infiltration can lead to the growth of mold and mildew, which can cause health issues and damage to structures. Waterproofing helps to prevent this growth, keeping your retaining wall and surrounding area safe and healthy.

Waterproofing Options

After assessing these factors, you can choose the most appropriate waterproofing method for your retaining wall. Some common waterproofing methods include:

Sheet Membrane Waterproofing: Sheet membranes are pre-formed waterproofing sheets that are adhered to the retaining wall. They provide a durable, water-tight barrier that is easy to install to provide continuity on the wall. This type of waterproofing is ideal for long term protection of the occupied space and the substrate.
Liquid Membrane Waterproofing: Liquid membrane waterproofing involves applying a liquid coating to the surface of the retaining wall, creating a seamless, watertight barrier. They are flexible and can be applied to a variety of surfaces. Liquid applied waterproofing is dependent upon the applicator and as a result, they should be fully trained in the installation of these types of materials.
Cementitious Waterproofing: Cementitious waterproofing involves the application of a cement-based mixture, as a slurry, to the retaining wall, forming a durable, water-resistant barrier. This method is relatively easy to apply and can be quite effective in waterproofing retaining walls. It is particularly well-suited for concrete retaining walls and can be used in conjunction with other waterproofing methods for added protection; however, it may not be as flexible as other methods, making it more susceptible to cracking over time.
Drainage Systems: Installing proper drainage systems, such as weep holes, perforated pipes, or drainage mats, can help to manage water infiltration and reduce the hydrostatic pressure on the retaining wall. These systems are to be used in conjunction with other waterproofing methods to provide an effective waterproofing system.
Integral Waterproofing: Integral waterproofing involves adding a waterproofing agent to the concrete mix used to build the retaining wall.
Bentonite Clay Waterproofing: Bentonite clay is a natural material that swells when wet, creating a watertight barrier. This method is environmentally friendly and provides excellent waterproofing. However, it can be more difficult to apply and may not be suitable for all types of retaining walls.

Remember, it’s crucial to consult with a professional waterproofing contractor or engineer to ensure the chosen method is suitable for your specific site conditions and retaining wall type. Proper waterproofing will help prolong the life of your retaining wall and protect your investment.

W. R. MEADOWS, INC. offers a range of waterproofing products for retaining walls, including MEL-ROL_® self-adhered waterproofing membrane, MEL-ROL LM, HYDRALASTIC_® 836, CEM-KOTE line of products, and MEL-DRAIN_® drainage products.

Expert Opinions

With regards to the “best” type of product, I would look at either MEL-ROL or MEL-ROL LM for this type of application. For the best overall system, use of either of these with the MEL-DRAIN as both drainage and protection would be my recommendation!”

When choosing the right product to use when waterproofing, you need to look at your wall construction. For example, if the wall is cast in place concrete, I’d recommend MEL-ROL and skim coated with MEADOW-PATCH TT or MEADOW-PATCH SMOOTH-GRADE depending on the finish, bug holes, pin holes, etc., and then appropriate MEL-DRAIN 502 or 5035. My rule of thumb is anything under 10’, MEL-DRAIN 5012 is fine; greater than 10’, I steer toward MEL-DRAIN 5035. If it’s masonry wall, joints need to be struck flush and so I’d go with MEL-ROL LM or HYDRALASTIC 836 with the MEL-DRAIN “B” boards of 5012 or 5035.”

The selection of a waterproofing system that is spray-applied versus sheet-applied, or use of another product, is all based on budget, supply, and/or labor. Fluid may be preferred simply because it’s monolithic, with no detailing except for joints, corners, or cracks; which is best for masonry walls, or a surface with lots of protrusions. It offers ease and a great barrier! I also like to recommend the use of a drainage board (MEL-DRAIN) as the standard for protecting the membrane.”

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To find out more about W. R. MEADOWS building envelope solutions, including our various Waterproofing Systems, please click here.

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Waterproofing a Retaining Wall

A Guide from W. R. MEADOWS, INC.