Understanding Active Soil

Reader Contribution by Kayla Matthews
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You may or may not realize it, but the soil beneath your feet is not as stable as you might expect. In some areas of the country, the geological composition or makeup of the soil can cause serious instability, particularly when it comes to the movement or shift of a building’s foundation.

A structure on a section of ground or soil with this issue can experience some severe damage and maintenance issues. Structural damage can occur to homes and businesses, causing problems with the walls, floors, windows and even interior. Floor tile may crack and warp, for example, or windows can become naturally sealed shut, never to open again.

Soil that moves or is unstable is called “active” or expansive because of how dynamic it is. There is a significant difference between active and inactive soil, including its composition and how environmental conditions can affect it. If you own a home, are considering buying one or planning to move properties — even as a business owner — there are some things you should know about active soil.

Why Soils Expand or Become Active

Expansive or active soils are a form of ground composition that expand and shift when they encounter moisture. When the soil or clay meets water, it expands, and when it dries out again, it shrinks. That creates a continuous pattern of activity and instability.

Imagine building the foundation or structure of a residence on top of that type of soil. It’s not safe or stable, and can lead to severe issues. Over time, significant damage to a structure on active soil will likely occur. These damages can include exterior cracks, hard to close windows and doors, wall gaps and floor tile cracks inside your home.

Experts estimate every year in the United States, expansive soils cause about $2.3 billion in damages to houses, buildings, roadways, pipelines and manmade infrastructure. Just as a comparison, this is more than twice the annual damage that results from natural disasters such as floods, hurricanes, earthquakes and tornadoes. It is both common and incredibly problematic.

What Buildings or Properties Are at Risk?

Unfortunately, any structure on active soil is at risk for damage. Expansive soils are present throughout the entire world, and the U.S. is no exception. There’s really no way to pinpoint areas that are more susceptible, either, at least not without comprehensive soil and ground composition tests.

What makes matters worse is that most people have never even heard of active soil or the problems it causes. It can go unnoticed, even in heavily affected areas. In some cases, people mistakenly attribute damage as a result of the phenomenon to other factors, such as shoddy construction or more natural forms of settling.

In short, all properties, regions and structures are at risk.

How Does Homeowner’s Insurance Fit Into the Equation?

Most homeowner’s insurance policies do not cover damage or issues caused as a result of expansive soil. That can be troubling, as the cost of repairs and maintenance can often get out of hand — in some cases, it may even be more than the total value of the residence or property.

If you spot the damage early, you can mitigate the costs. But therein lies the catch — most people don’t know enough about it to recognize symptoms, let alone be proactive about it. One homeowner may, for example, notice structural cracks and attribute them to natural settling. A few years later, they hire a painter to resurface the outside of their home, who fills up the cracks and makes everything look new again. All the while, the property damage is ongoing, with nobody the wiser.

By the time the issue truly becomes apparent — years and years later — the remedial costs have ballooned. And again, most insurance policies and providers don’t cover or deal with active soil issues, forcing homeowners to pay for everything out of pocket.

Is it Possible to Fix the Problem?

There are a few ways to deal with active or expansive soils, none of which are do-it-yourself remedies. That means an experienced professional will need to handle them. To start, it’s possible to develop a home or property with expansive soils in mind. That doesn’t help existing buildings, obviously, but some methods put newer properties at less risk.

A construction company can remove and replace the upper layers of expansive soil before beginning to build. Pre-wetting or expansion may be another step to ensure pressure is not further degrading the soil quality. Finally, structural and support underpinning methods can also help, such as grade beams or concrete piers.

For existing structures, structural slab or concrete injections may be in order. Calcium treatments can also help, which reduce the expansion potential of clay and similar materials once infused. Alternatively, soil stabilizers help prevent further expansion and shrinkage.

Finally, there are moisture control and subgrade irrigation measures to minimize the amount of moisture or fluids that pass to soil. Builders might add a perimeter apron or surrounding pavement slab around the home, after removing all plants and moisture-based materials. They may also implement better drains or cutoff walls. In addition, a construction company might redirect irrigation and watering sources.

In the end, it’s important to know there are some ways to improve active soil issues — even for existing homes and structures.

How Can You Tell What Areas Are Affected?

Expansive soils can be tough to identify, often because the surface composition tends to be different than the deeper layers of the ground. Active soil often contains clays, clay shales, and even porous sandstones that are susceptible to moisture and its effects.

Furthermore, the types of soils and materials differ regarding reaction. Certain types of clay, for example, may be able to withstand higher levels of pressure, which can give the impression it’s not active under certain conditions. Unfortunately, all affected soils and clays will heave and collapse eventually, which results in the movement responsible for structural damage.

That said, surface cracks in topsoil, wedge-shaped soil aggregates and easily crumbling soil grains can be direct indicators of expansive soil pockets or areas. But the absolute best way to identify and detect expansive soils is to conduct comprehensive lab tests — which requires an experienced professional.

The Ground Is Not Always Stable

As difficult as the concept may be to grasp, the ground beneath our feet is not always stable. That can affect homes, businesses and even massive structural complexes like apartment buildings, offices and hospitals. It’s always a good idea to get land assessed before building in any area. Not to mention, it will likely be cheaper to remedy an issue before a structure or residence is in place.

Photo credit: andres chaparro

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