First the bricks on Ed Cahill’s house started to separate.
He tried to fix the problem himself, but a year later the same thing happened again. The cracks began to appear on his interior walls, and the window sills began to sag.
When Cahill decided he and his Arlington Heights home had had enough, he called in Concrete and Steel Engineering, a Bartlett firm that specializes in righting wronged houses.
“I discovered that my house had sunk about eight inches in the span of just a few years,” recalls Cahill about the events he experienced six years ago. “It was ripping the place apart.”
When neighbors started asking about the construction work being done on his home, he learned that many of them were experiencing similar problems.
“It seems that many homes were built on unsteady soil,” Cahill says. The problem ultimately cost him $11,000 to fix.
“Sometimes the soil can’t handle the weight of a house, and it can settle to the point where it affects the physical structure of the building,” says Lauren Pate, owner of Concrete and Steel Engineering.
All buildings settle, though normally such settlement shouldn’t exceed about an inch. Extreme instances, like Cahill’s, may happen because the right soil preparation work wasn’t done before construction, according to Pate. In less severe cases, that can mean damages are limited to cracking in walls.
“These things can be fixed, but at a cost,” says Ed Weiner of the Concrete Doctor, a concrete restoration and engineering business in Prairie View.
Weiner estimates that damage from such settlement can cost a homeowner anywhere from $5,000 to $30,000.
In most cases, avoiding such problems starts with soil testing, the domain of the geotechnical engineer. Geotechnical engineers study subsurface soil conditions and look at how the land will hold up under the stress of a building’s weight.
Many developers say this work is important, whether you’re putting up a structure as tall as Sears Tower or a single-story suburban home.
“The soil condition can have a significant financial impact on a building project,” says Michael Machalinski, a geotechnical engineer for Testing Service Corp. in Carol Stream. “There are different measures for heavy, tall buildings and for houses, which are relatively light structures. But finding out what will be under a structure is important no matter what the size.”
Although the predominant soil in this area is clay, Machalinski says that the Chicago area has erratic soil conditions, meaning that the composition of the earth can change every 50 to 100 feet in any direction.
“In the north suburbs and west to Bolingbrook you’ll find a lot of clay,” says Machalinski. “As you move west toward the Fox River and south to Joliet, you’ll find more sandy soils or silt, which is a mixture of clay and sand with a high water content.”
In southern Wisconsin, there are granular soils, which tend to be somewhat looser than clay-heavy soils.
In Indiana, especially near the Dunes and around Gary, there are surface sands.
In an ideal world, all buildings would be constructed on ground that contains sand and gravel, or clay, according to Machalinski.
“I’d stay away from the organic soils, like peat, because they tend to be compressible and have a tendency to settle when a load is added to them,” Machalinski says.
At the same time, he and other experts agree it’s not so much a case of avoiding certain types of soil as it is knowing what’s there and adapting to it.
“In many cases, it’s not a matter that soil conditions are good or bad, because there are ways to work with all soils,” says Machalinski. Most geotechnical engineers agree that most any type of land can be built upon.
“You just have to have the money to do it,” says Elliott Drumright, senior project engineer for Soil Testing Service in Northbrook.
For example, if you want an 8-foot basement but have water in the ground at that level, the builder must do some extra soil preparation work to get past the water. It’s such a costly endeavor to avoid water that Machalinski says it’s often best to scrap plans for a basement altogether or to put the basement at a shallower level, say six feet, if that’s where dry land can be found.
If the buyer insists on a deeper basement, and “if you know this up front, you can make cost adjustments,” says Machalinski. The buyer, after discussion with the contractor, can agree to pay for extra digging and fill to prevent water-related problems, rather than waiting for the consequences of not doing such work.
Otherwise, he says, “afterwards, you either make costly repairs or live with the water.”
A good soil composition is any that can hold at least 3,000 pounds per square foot, says Machalinski. “Any less than that doesn’t mean you can’t build, it just means you need to do more work,” he says.
Typically, that means constructing a more elaborate foundation.
There are three basic types of foundations: shallow concrete footings, typically used in low-rise structures; wood, steel or concrete piles that are hammered into the ground; and concrete caissons that are poured to rest on a hard layer of rock. The last one is commonly used with taller, heavier structures, and can provide the most stability in otherwise unstable soil conditions.
When conducting soil tests, geotechnical engineers look at whether the earth is made from fill, which is a manmade composition, or whether it was formed by natural processes. Trouble can follow when a fill isn’t compacted properly..
Another source of trouble for builders, says STS’s Drumright, is low-lying, high-water-retention soils, such as clay.
“The more poorly drained, the softer and weaker the soil can be,” he says. Drumright says better-draining soils often are found on hillsides or hilltops.
The clay so prevalent in the Chicago area came from glacial deposits left here millions of years ago, and its physical distribution can include anything from small particles to boulders. The glaciers that moved through this area were so heavy that they compressed the soil. But glaciers, while heavy, are inconsistent, so some areas of land tend to be more compressed than others.
“Before we buy any land, we do a complete test of the soil,” says Joseph Cohen of the Zale Group, a developer of residential and light industrial properties. “We protect ourselves by making the outcome a clause in the option to buy. If it’s no good, we can’t use it.”
Cohen says the makeup of the soil can affect the cost of the project. “We have a development in Cary going on now where the soil is soft and easy to work with,” says Cohen. “On the other hand, we have a project in Kenosha that is a little harder because the soil is mostly clay and heavy topsoil.
Construction professionals, like Cohen, prefer that clay and topsoil be separate rather than mixed, because, they say, the elements are more stable when separated. A clay and topsoil mixture like that found in Kenosha can be even harder to work with in the spring and fall, when rains and unpredictable weather conditions can combine to destabilize these elements further.
William Rotolo, vice president of land acquisition for Concord Development Co. in Palatine, says the gravel and sand makeup of the soil in McHenry County makes land there generally good to build on.
“The gravel composition doesn’t hold as much water as clay,” says Rotolo. “If the land is grossly wet, we don’t like it because drainage systems are so expensive.”
As one might expect, much of the best land in the greater metropolitan area has already been built on, leaving some observers to comment that what is left may not be as good for building. This means that certain development projects in the future may require more expensive and time-consuming preparatory work to compensate for the less-than-ideal conditions.
If such construction projects don’t accurately assess soil conditions, or ignore them, the incidence of sinking or unusable structures will rise.
“It is rare that a structure is built that sinks so severely and unevenly that the entire thing is a wash,” says Rotolo.
It may be rare, but it does occasionally happen.
Take, for instance, the original Cernan Space Center at Triton College in River Grove. It was built in the late 1970s, and some years later engineers noticed that walls and floors were cracking and ceilings were sagging. After an investigation determined that the structure was destabilizing as the ground beneath it shifted and settled, the building was evacuated and permanently sealed.
Although a new Cernan Space Center went up nearby to replace the defective building, the original still has not been torn down.
In best-case scenarios, settling and sinking are not only accounted for, but actually built into the development plan.
One particularly creative example is the Cross Creek Building parking lot in north suburban Deerfield.
The 400-car lot, paved with asphalt and blacktop, is expected to sink from 6 to 8 inches over the next 12 years. Recognizing this, the project’s architects intentionally designed a slope into the landscaping around the building. The net effect is that cars always will drive down into the lot, but as the years go on, the descent will grow marginally steeper as the lot settles.
When buildings sink, their owners usually find themselves sinking into debt right along with them.
It can be well worth the investment to study the surrounding soil conditions and make adjustments accordingly. “If everyone does their job,” says Pate, “from the geotechnical engineer on up through the builder, a building should never sink.”
