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Can a little hole make a big difference?

Here in San Diego I have the opportunity to see a lot of retaining walls due to the type of terrain (hey, we're not just about beaches!). Since retaining walls typically hold back soil, it's likely that they are also holding back moisture in that soil. When the retaining wall is not built properly to allow that moisture to drain from the soil behind it, the retaining wall can deteriorate, buckle, and collapse, which is what is beginning to happen to the wall shown in Figure 1.

Stucco retaining wall damage  Figure 1. Stucco retaining wall damage.

There are two steps to the construction method that our builders here in San Diego leave out, and it doesn't matter whether the retaining wall has been built at a multi-million-dollar property or in the local tract subdivision. Builders always seem to omit these two steps:

  1. Install a vapor barrier behind the wall. A vapor barrier typically is simply a polyvinyl sheet installed against the back side of the wall to prevent contact with the soil and its moisture.
  2. Install drainage holes at the bottom of the wall, like that shown in Figure 2.

Stucco retaining wall drainage hole  Figure 2. Stucco retaining wall drainage hole.

I understand that we don't get much rain here in San Diego, which is why those two steps are often omitted, but what builders don't seem to realize is that the neighbor whose property is on top of the retaining wall wants to plant a lush green lawn, and such lawns in a desert environment will, indeed, require lots of water, water which will cause moisture damage to the wall in as little as one year.

When one has paid millions of dollars for a home in an exclusive subdivision, one can be slightly upset when that front retaining wall looks like that in Figure 1 after only one year.

Comment balloon 0 commentsTim Maitski • August 24 2008 08:32PM

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