How to Use Old Concrete for Retaining Walls


Building retaining walls using old concrete, also know as "urbanite," has many advantages. It can save you on the cost of materials and the cost of disposing of old concrete. It also prevents old concrete from filling up landfills. Old concrete chunks can be used to build effective and attractive retaining walls. The process has been so successful that, in some areas, businesses are being launched specifically to repurpose old concrete.

Things You'll Need

  • Old concrete
  • Constructon tools and materials (optional)
  • Decide where you want to build a retaining wall of urbanite, and whether you want to hire a contractor or tackle the job yourself. A long, high wall may need some professional tools and assistance. A typical garden or landscape wall can probably be done by a determined homeowner with shovel, rake and wheelbarrow. Get a supply of old concrete, some homeowners get their urbanite from an old driveway or patio they are replacing. You can also find urbanite by putting an ad in a newspaper or other publication.

  • Try to identify your concrete source before it is breaking it. This will allow you to have some control over the size of the pieces. Ideally, you want concrete broken so there is at least one fairly even face. It is best if it can be broken into fairly rectangular chunks. It is also best if there is not a lot of reinforcing bar or material, which generally will have to be removed. The best retaining wall concrete also will have larger aggregate (rock) pieces in it, rather than small gravel; this will give the wall a better, more natural appearance.

  • Check local building codes and permit requirements. Generally, a wall over four feet high will require some professional engineering, as will a wall with any major pressure behind it. Lay out a pattern for your wall, and dig a smooth, even trench several inches deep. The higher your wall, the deeper your trench must be dug. The width of the trench must be as wide as the widest concrete chunks to be used. Add a layer of sand to help you level your concrete chunks.

  • Lay the biggest, widest, chunks in the trench first, trying to keep the tops fairly level. Cover the first layer with about 3/4-inch of soil. Add layers of progressively smaller chunks, making sure to overlap joints. Step layers back, just slightly, instead of trying to lay them precisely vertical. Finish your top layer with chunks that have the smooth side up, and try to make the last layer as level as possible. Use a layer of soil between rows. You can also use concrete or mortar to bind the layers. In heavy soils, add backfill of gravel behind the wall to improve drainage.

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