It is said that practice makes perfect. A concert pianist would never dream of performing before an audience without first taking months to perfect his technique. Nor would a surgeon dare make that first incision without years of careful training and practice beforehand. There’s no easy, fast track around it.
It’s like what Tom Hanks’ character says about baseball in the movie, “A League of Their Own”— ‘if it was easy, everyone would do it.’ As a landscape contractor who designs and builds hardscapes, you may already be a master craftsman with many, many years of experience behind you. That’s good, because in your career, you’ll probably never build anything where precision and attention to detail is more important than when you undertake to construct a retaining wall.
Let’s face it: if you install a paver walkway and you or your crew makes a mistake in a section of it, you can always go back and fix that section. But a structural mistake in a retaining wall? Not so easy— the entire wall may have to be built all over again, and on your dime.
A retaining wall is called that because it retains a load; kind of obvious, right? It may be shoring up a hillside or keeping a home or other structure from being buried in a mudslide. If that wall should fail, not only would property be damaged, but people could be hurt, even killed.
We’re not trying to scare you… well, maybe, just a little. What we really want to do is emphasize the importance of having a good, solid plan and then, following it. In some states, such as Massachusetts, any retaining wall over four feet high must be designed by an engineer.
“The most common mistake a contractor can make in planning retaining walls is not hiring an engineer when codes require it,” said Karen Nelson, P.E., engineering services manager for VERSA-LOK in Oakdale, Minnesota. Required or not, if you’re not sure about the soundness of your design, have a structural engineer take a look at it.
No shortcuts Ian McNabb, a landscape designer with R. M. Landscape in Hilton, New York, has never had to rebuild any retaining wall he’s designed. “Any good retaining wall should last indefinitely,” he said. “I’ve never had to rebuild a stone or brick retaining wall, and I don’t think it’s because I do anything special. I just do it right the first time so it only has to be done once.” A good designer, he says, should be able to create specifications that any installation crew can follow.
There should be no shortcuts when constructing retaining walls. As we’ve said, mistakes made during the process can ultimately lead to wall failure. Dave Jensen, president of Jensen Retaining Walls, Omaha, Nebraska, knows this. He goes over and above the call of duty for his clients, and makes sure everything is done right. This helps him sleep well at night.
“First, you’ve got to pinpoint exactly what kind of wall is going up,” he said. “If you go by the specs, these walls will last a long time. But not if you cut corners—and a lot of people do.”
The most common example of a cut corner Jensen sees is when someone hasn’t dug deep enough prior to installing a foundation. “The bottom of a wall is where the most physical labor of the job is,” he said. “It’s important, for all of these walls, to do a bit extra, not just get by. If there’s a flaw at the bottom, it
might not show up today, or even the year after that, but it will show up.”
The biggest enemy of retaining walls is water. Hydrostatic pressure building up behind a wall is the number-one cause of failure. So, make absolutely sure you design with adequate drainage.
The first day of the job shouldn’t be the first day you set foot on the worksite. Scout the location thoroughly before starting. Check out any regulations or restrictions that could apply. The middle of a job is not the time to find out you should have gotten the approval of the homeowner’s association first.
Then, do a thorough analysis of the site. The wall will stand or fall depending on how well you do this, and follow up on your findings. Every wall is different, because every location is different. The quality of the surrounding soil is critical. It may need to be amended before you begin.
The next step is to create a budget. There are numerous variables that will influence the cost, in addition to the wall’s size and the type of materials used. Cost of excavation, for instance. Will you need to rent equipment, or do you already have it?
Labor will probably be your largest cost, after materials. How many people will you need to complete the job on time? Do they already work for you, or will you need to hire extra?
“The job’s location is one of the most important factors to consider when planning a budget,” said Jensen. “You might be working in a place where access for the machinery is difficult.” The ease or difficulty of getting tools and machines to your worksite will make a major difference in the price.
“Make sure you plan for the unexpected,” said Matt Singer, director of national sales and training for VERSA-LOK. “And always build wiggle room into your budget to meet challenges, such as availability of supplies, equipment or labor.”
Last, but certainly not least, are the materials that will be used to build the wall. This will affect the final price tag of the project more than anything else.
Materials As the contractor, you may or may not have input into what materials will be used for building the wall. What you need to determine, however, is whether the materials fit the budget or not. If the client has his heart set on bluestone but has only budgeted for brick, then it’s time for a discussion.
Cost isn’t everything, of course. For example, a relatively inexpensive retaining wall could be constructed out of untreated pine. However, the material’s limited lifespan doesn’t make it a cost-efficient choice.
Retaining walls can be built out of any number of different materials. Some of the most common include stone, brick, articulated concrete block, concrete with stucco finish, and pressure-treated wood timbers (fir, cedar and redwood). A determining factor when choosing materials should be whether a wall will be merely decorative, used for structure, or both.
Price of materials varies by region and production levels. Manufactured materials, such as brick and concrete pavers, are usually much less expensive than quarried natural stone or fieldstone.
Natural stone is a material that’s in a class by itself. “Retaining walls built with natural stone are an art— almost a lost art,” said Singer. Most contractors agree that natural stone—even if you were able to get it at a bargain price—is the most expensive material, as it requires a higher skill level to install, and is more labor-intensive. It’s mostly used on higher-end projects.
Using two or three different color blends of natural stone can make a wall appear as if you’ve cut into the side of a rock mountain and are seeing the natural striations.
Natural stone can be used structurally in two different ways. Wet stone is best used when you need to hold back a large volume of earth. It uses mortar to provide extra stability. Dry stacked stone fits together without using any form of fixative and is used most commonly for decorative walls.
There is another type of retaining wall that might have appealed to the Great Houdini himself. This type of wall performs a magic trick: over time, it disappears!
This is the “living” retaining wall, so called because it is, in a very real sense, its own ecosystem. Living walls incorporate pockets filled with growth media where either seeds or plant plugs can take root. As the vegetation grows over it, the wall is eventually concealed.
The increasing interest in ecogreen, sustainable, environmentallysound landscapes and buildings has spurred the popularity of living walls. As a result, in the last few years, many companies have sprung up that specialize in making innovative building materials expressly for living walls. Two common materials for blocks are articulated concrete and polyethylene.
These living walls will require some sort of irrigation system. Usually, drip systems work best. Again, we must emphasize the importance of building in a good drainage system. It’s especially vital here, where water is being incorporated into the design.
When a retaining wall is part of a larger project
If you’ve been in the business for any length of time, you know that hardscape fashions change. If you doubt this, just look at an old homeimprovement magazine from the ’70s or ’80s. Keeping up with changing tastes is part of the job.
One of the growing trends is the increased demand for outdoor living spaces. When industry surveys are done, outdoor living rooms and kitchens—often complete with televisions, professional ranges and refrigerators—always top home-owners’ wish lists. Retaining walls are part of this trend.
Not surprisingly, this has changed the way retaining walls are built. It’s not that the construction methods have changed; it’s what the walls are used for that’s been transformed. An element once valued solely for its functionality has evolved into a creative accessory. A project can begin with a need to replace an old, perhaps crumbling retaining wall, and expand into something much more ambitious.
Retaining walls aren’t just functional solutions for stabilizing sloped terrains and preventing soil erosion any longer. Landscape designers, architects and home builders are incorporating these walls into their designs for their aesthetic value alone.
A beautiful wall can enhance a sense of privacy and security. And clients are beginning to see a greater value for retaining walls, besides erosion control prevention. A decorative retaining wall can be the focal point of an outdoor living room or kitchen, or as a backdrop for seating.
When a wall is part of a larger-scale hardscape project, such as an outdoor kitchen or living room, you really have an opportunity to be creative.
Columns, accent lighting, built-in seating, decks, multilevel patios, fire pits—the list of enhancements goes on and on.
One thing that really can make an outdoor living space “sing” is a striking focal point—a single element the eye is instantly drawn to. Maybe it’s a fountain, a fireplace, a sculpture, a large boulder, or an especially striking or unusual tree or bush. Sometimes the wall itself is the focal point.
Before Blu Wahle, owner of Wahle, Inc., in Underwood, Iowa, begins any hardscape job, he talks with his clients in detail to understand “the root of their story.” That is to say, he finds out exactly what they want to use the outdoor living space for, and then creates a plan from there. Here again, everything starts with a great plan.
“It might end up saving them money, or it might not, but they’ll be happier in the end,” Wahle said. “Create a space that is really appealing and they’ll use it more.”
We hope we’ve shown you that retaining walls can be both functional and beautiful at the same time. It all depends on what your client wants, and how you build it. It isn’t easy, but you’re more than capable, if you plan it right.