How to Seal Retaining Walls

Updated February 21, 2017

Retaining walls hold back earth or water, providing open space on the other side. The construction of a retaining wall is similar to that of general foundations. And they require the same kind of maintenance to prevent moisture seepage and inevitable discolouration.

Clean the wall thoroughly, using a power wash system or a bucket of warm water and a scrubbing brush. The wall needs to be both clean and clear of debris, such as dirt and mortar. Allow the wall to dry thoroughly overnight.

Pour waterproof primer, which will act as a sealant, into the paint tray. Roll the paint roller through the primer, and squeeze off the excess on the side of the paint tray. Apply even coats of primer to the wall, using the paint roller. Wait an hour for the primer to soak in, and then apply a second coat evenly with the paint roller. Wait 24 hours for the primer to soak in and dry completely.

Examine the wall for cracks and holes. Fill these with liquid rubber. Smooth the surface around the repair, using a putty knife. Follow the instructions provided with the liquid rubber. Apply an even coat of waterproof sealer to the wall, using the paint roller. Fill in any uneven areas with the paintbrush and more sealer.

Wait two hours for the sealer to dry and set properly. Apply another coat of sealer evenly to the wall, using the paint roller. Allow this coat to dry, and then apply another coat. Again, go over uneven areas with a paintbrush to ensure that the sealer has worked into all the nooks. Allow 24 hours for the sealer to dry thoroughly. Apply a coat of concrete finisher evenly to the wall, using the paint roller.


If the retaining wall is still under construction, it is worth taking the time to attach a sheet of thick plastic to the back of the wall before infilling with soil or other material. This will give the wall an additional moisture barrier and help it last longer.

Things You'll Need

  • Bucket
  • Warm water
  • Scrubbing brush
  • Waterproof primer
  • Paint tray
  • Paint roller
  • Liquid rubber
  • Putty knife
  • Concrete finisher
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About the Author

Based in the United Kingdom, April Kohl has been writing since 1992, specializing in science and legal topics. Her work has appeared on the Second Life News Network website and in British Mensa's "LSQ" magazine. Kohl holds a Bachelor of Science in physics from Durham University and a diploma in English law from the Open University.