Do-It-Yourself Retaining Wall

House Doctor | Gary Dymski

September 14, 2000

THERE WERE A few problems when the builder finished our new home in 1997. Most were minor touch-up things you'd expect in this era of hurry-up construction. We didn't, however, expect our backyard to end in a slope of nearly 20 feet.

Because we had plans for an in-ground swimming pool, we knew at some point we'd have to eliminate that slope. The time came this summer, when pool plans were completed. And after I received a few estimates from contractors, the decision was easy: I decided to build the retaining wall myself.

Because of the odd-shaped and poorly graded building lots you find on Long Island, chances are you've seen plenty of these walls. They're used for everything from leveling property to eliminating erosion.

To increase backyard space on our half-acre lot, we needed to construct a wall of at least 4 feet in height and more than 125 feet in length. It would cost from about $3,500 for a wood wall to nearly $15,000 for one of stacking stones. A cinder block wall would cost about $5,500.

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After some research, my best choice was the preformed stacking-stone system. It was relatively easy to build (if you were Superman, I would find out), durable and would fit on my credit card.

Wood was out because it would have to be replaced in about 10 years. Cinder block with a stucco finish was not attractive enough, too labor intensive, and I had concerns about stability. (Cinder block walls have a tendency to tilt.)

Now, I know better than to be sucked into the HGTV syndrome, as Gino DeFrancesco calls it. "They make everything look so easy when they show homeowners how to do something on TV," says DeFrancesco, 35, a sales associate at All-Island Mason Supply in Kings Park, where I eventually purchased the stones for my wall.

Exactly. Every job site is perfect; they have all the tools, all the help, all the time. Take it from me, though: No job ever has perfect conditions. But I like to think I can do nearly everything around the house, and I've tackled tough jobs before.

"Because these retaining wall systems are pretty easy -- it's all heavy labor, really -- we find that a lot of homeowners are trying them," DeFrancesco says. "The hardest part of any stacking system is setting the first row. Once you've done that, they go together pretty quickly."

I would be building a wall out of stones that weigh nearly 70 pounds apiece. I needed anywhere from 750 to 900 stones (that's hauling and setting between 59,500 and 63,000 pounds). Plus, I would have to build a level footing out of crushed stone.

I had several options regarding stacking stones, but two things concerned me; the weight and size of the stone and my access to the job site. Heavy stones, some as heavy as 100 pounds, would be harder to work with and move manually to the base of the wall. I needed a stone I could easily carry or move by wheelbarrow.

I settled on a 6-inch-high stone made by Grinnell Retaining Wall Systems in Sparta, N.J. Since I wanted a wall that would end by turning into another small slope on the east side of our property, I chose Grinnell's Diamond Beveled Unit, which is designed for straight walls and those with inside and outside corners. Using information supplied by the manufacturer, I determined I would need 756 stones. First mistake. I would find near the end of my job that I was short by about 150 stones. Each unit cost $5.13, compared to about $7.50 to $8 for the larger, 8-inch stones. Add $100 for delivery, another $100 for 5 yards of crushed gravel.

Two other problems surfaced. We had the pool built before building the wall. Our slope had disappeared, replaced by a mountain of sand left over from the hole for the pool. We kept the dirt to use as backfill for the wall. I had to hire a landscaping company to dig a 5-foot-wide by 100-foot-long trench for the wall. Then it was my turn to dig a level trench 2 feet wide and 6 to 8 inches deep. It would be filled with crushed gravel, then tamped with a power tamper ($56 for a 24-hour rental), creating a foundation for the wall. Over the crushed gravel I would lay a 2-inch bed of sand, then begin setting the stone.

I caught a major break; my neighbor recently had a mason build a cinder block retaining wall to eliminate his slope. I could begin my wall by simply stacking the first row up against the base of my neighbor's wall and extending the existing wall line to the end of my property.

Remember the part about every job looking easy on TV? Well, the power tamper worked great. Except every time I ran it a huge layer of sand would tumble down, destroying my flat, level bed. I decided to tamp everything I could get to along the wall line, then I would scrape away sand as I worked down the line of the wall.

Of course, more goofy stuff happened. I set the first six or eight stones upside down. The Grinnell brochure shows the stones with the bottom side up. The bottom side features a lip at the back edge. "A lot of homeowners doing their own installations call about that," DeFrancesco says. "Nowhere on the brochure does it indicate that the stone is pictured bottom side up."

Leveling that first row (more than 100 stones) was difficult. In my case, it had to be done in two steps. Since I had one access path, I had to lay about two-thirds of the first row, build as much of that portion of the wall as I could, then finish the final third.

I started setting stones on July 17, the second week of my vacation. I finished the first week of September.

My oldest son, Al, who is 17, helped me most, digging part of the trench, laying gravel and carrying about half the stones to the base of the wall. I set every stone, 908 of them, about 63,000 pounds. Total cost was about $ 6,000, including a masonry saw blade for cutting some of the stone and decorative caps for the final row.

"I didn't think you could do it," my wife said. (She always says that.)