ailing retaining-wall
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Q: Each year, the concrete-block retaining wall in my backyard leans a little bit more. Can you tell me how to repair it?
—Ruth Besel, Ft. Collins, Colo.

A: I suspect that your wall doesn't have a proper footing, so it can't resist the expansion and settling of the soil that happens with each freeze-thaw cycle. In other words, the soil is slowly pushing the wall over.

The only way to install a proper footing is to demolish the wall, dig down to undisturbed soil below the frost line, and pour a thick concrete pad filled with rebar. Check with your local building inspector for the right footing depth for where you live, and have a soil engineer specify the footing size.

The easier alternative is a segmental wall system made of interlocking concrete blocks. These are solid blocks, unlike the ones in your wall, and need no mortar. That means the wall is relatively easy to assemble and is flexible enough to cope with freezing and thawing soil. Plus, it only needs a shallow, crushed-stone base; you don't need to dig below the frost line.

Whichever type of wall you choose, make sure water has a way to drain from the side against the soil. That's why I always install filter fabric, a drainage pipe, and clean drainage stone behind my retaining walls.
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