I've been building landscape retaining walls for about thirty years—about two-thirds of my life. While I can't say I've gone back and personally inspected each and every one of these landscape walls in the recent past, I can say I've never had a client call saying their wall tipped over.

During the last ten years, I've owned a landscape business, built dozens and dozens of retaining walls, and not a single call. During the previous fifteen years, I worked for a single small company and, once again, no calls about retaining wall failures… and we built a lot!

Throughout my thirty years in landscape construction, I've watched many retaining walls be built around the Madison area—and I've watched many retaining walls fail. There are numerous reasons but I find one quite interesting.

Historically, most landscape retaining walls were built with a setback or "batter," where each course of stone was set back slightly from the one below it, resulting in a wall face that leaned into the slope. These were typically considered "gravity walls"—they used their own weight to counteract the outward forces of the soil behind them. It's been done for thousands of years. And it works!

I earned a Bachelor of Science degree in Landscape Architecture from UW–Madison, and the construction details we were taught always included setting back each course of stone or block into the slope. I also earned a Landscape Horticulture degree from Milwaukee Area Technical College (they had a great program in the late nineties), and the message was the same: retaining walls should have a slight setback.

I've worked with several amazing stone craftsmen—guys who restore Frank Lloyd Wright properties and similar. The message is always the same.

More recently, though, there have been "innovations." Some of them are truly wonderful. Incorporating geogrid reinforcement behind a wall, for example, is honestly an engineering marvel. Simply installing a woven plastic reinforcing grid into the slope in layers behind a wall does amazing things to reduce pressures on the structure—it's a great technology and should be used on all walls over 3' or so.

Yet, I believe we still need to keep the lessons of the past in mind. If we combine time-tested gravity wall principles with geogrid reinforcement, we should be able to build walls that last a lifetime.

What seems to have happened instead, though, is that product manufacturers, contractors, and unsuspecting homeowners are relying too heavily on the geogrid approach and really pushing the limits of physics. Or worse yet, they aren't using the geogrid at all because they don't see it or understand its effect.

The new trend lately is building retaining walls perfectly vertical. Rather than incorporating a slight setback that effectively leans into the slope—much like you would lean into a door you're trying to hold closed against a flood—people are building them straight up. And sure, it looks nice and modern, and may require less cutting of pieces…

But I don’t get it!

These walls can certainly look handsome—especially at first—but there's truly no margin for error! There are many potential forces acting from behind a wall, some of the largest being:

The surcharge (weight) applied to the ground above the wall
The surcharge weight of the soil itself if the area slopes down toward the wall
Water pressure from trapped moisture freezing and expanding in winter
Expansive soils (like clay) that shift depending on their moisture content

In contrast, there are very few forces acting on the front of a wall—unless someone leans against it, there’s a really heavy wind, or maybe a tsunami (unlikely in Madison, Wisconsin).

Beyond these forces, there's always a chance of settling. If the materials below the wall contain organic matter that decomposes, the wall may sink.

Or maybe there's a bit of a sinkhole happening. (Anyone who doesn’t think underground voids exist should consider Cave of the Mounds—just west of Madison.) Large underground caves aren’t common here, but we frequently see similar issues on a much smaller scale near newer homes.

When homes are backfilled—especially in winter with frozen materials—they are not effectively compacted. Anything built above is prone to sudden settling in the future, particularly during late winter’s freeze-thaw cycles.

The Problem with Vertical Walls

So, there are numerous factors that can cause a retaining wall to shift forward, but very few that would cause a wall to settle backward into a well-compacted slope.

(Quick tangent: I recently read an article about earthquakes in Naples, Italy, where the ground is literally rising due to seismic activity! According to the article:

“The last time the area experienced ‘positive bradyseism,’ in 1984, the ground rose 3.5 meters (11.5 feet) before descending.”

The article was called "Naples Residents Camp Out After 4.4 Magnitude Earthquake Hits Amid Weeks of Seismic Activity"by Barbie Latza Nadeau, CNN. If you’re interested, it’s worth checking out.

I’m hopeful we won’t experience much seismic activity in my lifetime in Wisconsin, but according to Wisconsin History(accessed via AccuWeather, 3/17/25), there have been some events worth reading about.)

My point is: something always happens sooner or later. Maybe the wall shakes just a tiny bit forward, and the gravel or soil behind it fills in, holding it slightly beyond vertical. Then something else happens—maybe a really heavy rain event saturates the soil behind the wall, exerting even more outward pressure.

Nothing is going to push it back.

It may stand for years, but it will never be as stable as a wall slightly battered into the slope. Or, like many walls in Madison, it may begin to fail within a season or two.

Final Thoughts

Nearly all forces are pushing outward on a retaining wall. My approach is to use a time-tested method to push back and balance those forces. That’s what I would recommend 100% of the time:

Don't build a retaining wall vertically unless you really know what you are doing—build it to slightly angle (batter) into the hill.

I recently saw a wall near Monroe Street that seemed to be intentionally doing the opposite. The property is on a corner lot, and the exterior wall corner is built like the prow of a ship—not sloping into the hill as millennia of experience would suggest, but instead pushing outward.

It'll be interesting to watch.

If you're considering building a retaining wall, I encourage you to research gravity walls and think about whether the "Old Fashioned" approach makes sense. I’d be happy to talk about it!