The rules of building retention

The rules of building retention

Features - Design/Build

Retaining walls can be a profitable addition to your landscape service profile, but there are some important considerations to keep in mind.

April 7, 2014
Lindsey Getz
Industry News

There’s a lot that goes into building a successful retaining wall, and those who underestimate the required steps and skills are putting themselves at risk. A faulty retaining wall is not only a risk to reputation, but a significant liability. Understanding the engineering principles of segmental block wall installation is critical to the wall’s integrity, says Keith Frederick, president of Environmental Landscape Associates based in Doylestown, Pa. Those who are successful building retaining walls understand a number of elements and how they work together for construction.

“Proper base materials and compaction, proper backfill materials and ratios and correct drainage are all key elements,” Frederick says. “The biggest mistake new installers make is thinking a wall is simply a matter of putting in the base course and stacking it up without understanding the hydrology or soils of a site.”

At the base.

When it comes to something as important as a retaining wall, you should never cut corners, says Scott Shorrow, president of Landscape Concepts in Frederick, Md. For instance, geogrid is used for reinforcement but because it’s expensive to buy in a large roll, Shorrow says some contractors might be tempted to skimp. Shorrow says that’s a big mistake. “If the retaining wall calls for six-feet of geogrid, we’d be more likely to cut that at 6.5 than to short it,” he says. “I’d rather put some extra in than cut it too short. I call geogrid ‘cheap insurance’ and we put a layer or two of it into every wall.”

It can definitely be argued that the most important part of a retaining wall is its base. Les Cline, co-owner of Teacher’s Landscaping & Irrigation in Olathe, Kan., says that the most common source of wall failure he’s seen has been due to inadequate foundation. “Designing and installing a proper base is essential for the long-term viability of your project – and your reputation,” Cline says.

Failing to install a proper base is a common but detrimental mistake made by first-timers. “Any of the major manufacturers’ wall systems will produce a nice looking finished product but unless the base prep is done correctly, it is both a waste of time and money for the contractor and the client,” says Ed Swietanski of Gill’s Landscaping in Mullica Hill, N.J. “Underestimating both the cost of labor and materials to do a proper base install is also a common mistake. Think about accessibility to the site, soil conditions and other obstacles such as tree roots and irrigation systems that will add time to your project.”

Swietanski says that cutting corners on the base puts the company’s reputation at stake. “The base is the part of the project that no one sees and rarely gives it a second thought – until it fails and the whole wall has to be rebuilt,” he says. “You have one shot to do it right. The second time is twice as hard and much more costly.”


Get creative

There are times that erosion and land grading may force the need for a retaining wall. While the addition of a wall might be an unwanted necessity, there are some ways to make the wall more appealing. Contractors who are willing to get a little creative may have even more success within this service offering.

Smart design has a lot to do with how the retaining wall will look within the rest of the landscape. Strategic plantings can play a part in dressing up – or even distracting from – a retaining wall, though soil compaction and root zone issues need to be taken into account. “Some plants with light root structures could be planted at the top of the wall and allowed to grow over the fronts to soften the overall impact,” says Keith Frederick, president of Environmental Landscape Associates based in Doylestown, Pa.

Contractors who have gotten creative are also making use of the green, plantable walls now available, says Scott Shorrow, president of Landscape Concepts in Frederick, Md. “These walls have plant pockets that allow plants to actually grow within the wall,” he says. “The plants usually have to be lower maintenance – high heat tolerant and drought resistant – though some more complex systems can actually have the irrigation system tied into the wall.”

Sometimes just the shape of the wall can up the creativity ante. “Even with more commercial walls, you can still get creative with some curve instead of going totally linear,” Shorrow says. “A curved wall offers some interesting appeal.”


All about education.

Getting the proper training is a key to success and an important step to take before tackling a build. “Get training and get certified by a reputable organization like the National Concrete Masonry Association (NCMA) or the Interlocking Pavement Institute (ICPI),” Cline says. “Segmental retaining wall manufacturers also have training classes offered through their vendors. Ask to be notified when these classes are offered.”

Shorrow says he places a lot of emphasis on internal education, as well. “We are constantly training our people,” he says. “We spend a lot of time on safety training and making sure everyone knows the right way to lift a block. Safety training helps prevent accidents. It’s also important to make sure workers are proficient and good equipment operators before sending them out to build walls.”

Often the biggest lessons do come with that first build. If you’re just starting out, Cline suggests taking a “manageable project” for the first job. That would be one that isn’t too large or has too many variables. “There are things you can learn from building your first wall that you cannot learn anywhere else,” he says. “You just need to get some experience under your belt.”

Of course, education isn’t just for the newcomers. Cline says that even veteran wall builders should consider classes and ongoing education.

“It never hurts to keep your training up to date,” he says. “Things change and a professional should be on the top of his game at all times.”



Taking the proper safety precautions is important, but a step that is sometimes underestimated by landscape contractors who are new to working in the hardscape world.

“Respiratory health is a big health and safety issue that continues to be on the forefront of paver and wall installation safety,” says Frederick.

“When cutting pavers or blocks, always wear an approved respirator. The potential for lung damage is very high risk.” Beyond that, Frederick says the standard construction safety advice should always apply.

“Wear work boots, preferably with steel toes,” he says.

“Wear gloves, heavy duty long pants, and no loose fitting clothing. Helmets are always a good idea on a construction site, but especially when heavy equipment is moving materials around.”

“A lot of the common mistakes boil down to cutting corners and that’s true of safety precautions as well,” Shorrow says.

“Never cut corners on the proper safety equipment. It can result in injured employees and workers’ comp issues. For instance, a contractor should not be wearing sneakers to lift block. A dropped block could easily break a foot.”



circular retaining wall designA hardscape dream come true

John Fields took a simple project and turned it into an award-winner.

By David Aquilina

In October 2011, when the owners of an elegant brick home in Clyde, N.C. contacted John Fields, president of Haywood Landscapes, they had a modest project in mind. They wanted a small, manageable area to start a vegetable garden. When Fields stepped outside through the French doors from the home’s great room, he surveyed an inspiring vista of rolling hills with the Smoky Mountains in the distance. He envisioned greater potential.

“I saw an opportunity to extend the features of the home out into the landscape with a series of terraces connecting upper and lower levels to create a pleasant flow of beautiful outdoor living spaces interspersed with garden areas,” he said.

Fields’ vision captivated the homeowners. They gave him the green light to develop a plan to realize his concept. In November 2011, Fields brought in colleagues from Broadbooks Associates, P.A., a landscape architecture firm. Together they came up with two alternatives. The homeowners selected a circular design with curved hardscaped areas defining the series of terraces.

Challenges emerge. The project got underway in January 2012. A significant problem was quickly revealed.

“An existing patio area surrounded the great room on three sides. When we cut back the overgrown shrubbery around it, we found troublesome cracks in the retaining wall attached to the house,” Fields said.

Several areas of the wall were failing, allowing water to seep into the home. Moreover, the footer was undersized, and the deck tied into the patio was deteriorating. The best course of action was to remove and replace the retaining wall, patio and deck, which is engineered the area for new construction to solve the structural problems. A new drainage system was devised to direct water away from the new retaining wall as well as to manage runoff from the new hard surfaces to be constructed.

“The revised plan solved the structural problems of the existing footprint,” Fields said. “It had the added benefit of better integrating the new construction with the existing area.”

Before you enter

Think ahead.

That’s the advice John Fields has to any contractor thinking about entering the 2014 Hardscape North America (HNA) Project Awards competition.

Fields, president, Haywood Landscapes, won for his “Where Edibles Meet Hardscapes” project that took home the prize in the Clay Brick - Residential category.

“As you are working on it, start thinking about how you will summarize the challenges and highlights,” he says. “You also need excellent, professional photos that show the scope and details of your project.”

The program encompasses 22 categories, organized by material: clay brick and concrete pavers (conventional and permeable) and segmental retaining walls. The categories are subdivided by project type (residential, commercial, industrial and municipal) with some including additional subcategories by size. 

The institute will issue the 2014 call for entries in May. Jessica Chase, director of marketing and membership for the Interlocking Concrete Pavement Institute says contractors should start by assembling information and high-quality photos that showcase their best projects.

Submissions require a 250-word summary. Summaries that define project goals, explain design and installation challenges and highlight solutions and results help judges as they review project photos. “Even as the project was underway, I knew it was special and deserving of national recognition for my team,” Fields says.


A vision realized. Construction took seven months and was finished in July 2012. The completed project has five levels extending out and down from the rear and sides of the home. It provides space for edibles, installed alongside ornamentals, made accessible by a series of walkways and retaining walls that are functional and stately.

The existing upper patio (1,275 square feet) was redone with new pavers in a traditional herringbone pattern and a new 20-by-10-foot composite deck. The dark brown color of the composite material complements the bricks.

The project added 1,325 square feet of new hardscape, more than doubling the total hardscaped area. The new lower levels feature interconnecting walkways, two patios and four retaining walls. Multiple paving patterns create a delightful design. Subtle night backlighting accents the retaining walls and pavers for a visually engaging effect.

An additional 1,300 square feet is devoted to fruits and vegetables. With multi-level gardening, the plants can be easily accessed and tended to from above or below each terrace.

What was Haywood Landscapes’ biggest accomplishment? After 26 years of never having even owned patio furniture, the homeowners are now avid backyard entertainers.


The author is a freelance writer in Minneapolis.