Why Is This Retaining Wall Failing?

I walk by this wall whenever I walk to the post office in downtown Culpeper. Walls like this are pretty common in older neighborhoods like mine. Leaning and generally unhappy walls are, sadly, pretty common as well. So what gives? Why do these walls look like they’re ready to flop over on the sidewalk?

There are several possible explanations. The first is insufficient footer, or failure to tie the wall in with the footer. When building a masonry retaining wall in Virginia you generally want to dig down 24″ below grade, so you’re below the frost line. You then pour a beefy footer (thickness varies depending on application), often with rebar coming up from the footer to tie the wall to the footer. Our home was built in 1906 and renovated in the 1950s, and I can tell you with certainty that there was not a lot of digging to frost depth being done way back then.

Another possibility is insufficient drainage behind the wall. Water is a wall’s worst enemy. Hydrostatic pressure is a major cause of wall failure. The way we avoid a buildup of pressure is by using a “drainage chimney” of clean gravel behind the wall, along with periodic weep holes.

What makes this wall great for illustrative purposes is the fact that the wall likely started to fail because of hydrostatic pressure (water buildup behind the wall). This pushed the top of the wall forward, creating a gap between the wall and the slab. What’s right above the slab? Downspouts! So not only do we have a gap, we’re pouring gallons upon gallons of water behind the wall with every storm. Awesome.

So how would I fix this wall? I think we’re beyond the point of fixing something like this, and it needs to come out. Improper construction is hard to correct, and when it gets this bad – there’s no Band-Aid big enough.

Dave Marciniak is a landscape designer and speaker. He lives in Culpeper, Virginia and can be found via his website and on Twitter.

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