While not as intense as earthquakes, expansive soils are the #1 geologic hazard in the USA. They are responsible for more financial loss than other natural disasters combined. These soils also are behind many of the structural problems and damages that homeowners face.
Florida isn’t particularly known for expansive soils but there are areas that have soils with about 50% swelling potential. Don’t assume you’re safe. This article will cover everything you need to know about expansive soils, signs, and what steps you can take to limit their potential to cause damage.
Expansive soils refer to soils or rocks that contain minerals that can absorb water. They have the potential to swell or shrink under changing moisture conditions. When these soils get wet, they increase in volume.
The soil volume will keep increasing as they continue absorbing water until the soil gets saturated. Sometimes, these soils can expand by 10% or more.
Different types of soil have different minerals. Some have clayey minerals that swell, others don’t. Typical expansive soils have these minerals:
The swelling potential of expansive soils depends on their initial moisture content, dry intensity, soil stratum thickness, above the ground load, and degree of saturation.
A change in water volume can exert significant pressure on your building, leading to structural damage.
The force from the swelling soil can cause foundation or crawl space walls and floors to crack. When the soil loses water during summer months, it shrinks and removes support. This loss can cause soil settlement, which is a leading cause of structural deformations and foundation settlement.
The cycle of swelling and shrinkage isn’t good for your home as it can also cause foundation cracks and fissures. These openings may let in water into your crawl space. Water will instigate many problems including mold growth, wood rot, and water damage.
Swelling soils won’t go for long without getting noticed. Telltale signs that your foundation has expansive soils include:
Expansive soils can cause serious damage when they absorb and lose moisture content repeatedly.
Typical soil stabilization solutions include:
Moisture control: With this method, the foundation repair contractor attempts to stop surface water from seeping into the foundation by installing moisture barriers and sub-surface drainage around the perimeter of your home.
Foundation reinforcements: If your home is settling, the best way to stabilize and potentially lift it back to its original position is to install a piering system. Durable options include push piers, helical piers, and slab piers, depending on your type of foundation and repair needs.
Cement treatment: This building material is an effective stabilizing agent. It’s widely used to treat clay soils. Cement reduces the liquid limit and the plasticity of expansive soils and increases their strength.
Lime treatment: Lime is injected directly into the swelling soil. Hydrated lime reacts with the clayey minerals in the soil, reducing their plasticity and the soil’s swelling potential.
Chemical Injection: Expansive soils can also be treated using injection methods. First, the ground is injected with water to pre-swell it, then a chemical solution like potassium is applied. Rigs with multiple injectors are used to deliver the stabilizing fluid.
Reinforced slab-on-grade: If you’re building on expansive soils, design and create a strong and rigid foundation that can withstand soil shifts and isolate your home from the swelling soils. You can do this by installing a reinforced slab-on-grade stiffened by a grid of underlying crossbeams.
Landscaping: Proper landscaping can reduce the impact of swelling soils by limiting the volume of water that goes into your home’s foundation. Flowers and garden plants should be planted at least five feet from the foundation and be drip-line watered. Trees should be at least 20 feet away as they tend to absorb a lot of water in dry weather, which can reduce soil moisture content and disrupt the soil grading.
Damages arising from expansive soils are complex and often costly to repair. Some remedies only act as band-aid fixes, which mask the signs and fail to treat the root problem. Before you build your home, ask your foundation repair contractor to assess the soil to see if it’s stable.
Swelling soils don’t have to signal the death of your foundation. As long as they remain dry or maintain their moisture content, your foundation will be fine. The only time you should be worried is when these soils swell and shrink in cycles.
Get in touch with Florida Foundation Authority and discover the best way to fix your expansive soil problems. Our team has extensive experience in stabilizing homes, so we know what works and what doesn’t. Request a free foundation repair and inspection and get a solid recommendation to save your foundation and home!