Sinking foundations are common—in fact, most buildings will settle over time. The slow process of a building “getting comfortable” as the soil below it adjusts to the structure’s weight is typically no cause for concern. However, differential settlement, which happens when the soil beneath the foundation erodes away or moves unevenly, can cause severe structural damage.
Here, we’ll discuss the different types of settlement, their causes, symptoms, and solutions. If you’re afraid that your home’s foundation is settling, call AquaGuard today! We’ll schedule a free inspection, during which we can thoroughly assess your foundation for damage and recommend the best foundation repair solutions for you.
What is Foundation Settlement?
Foundation settlement happens when soil moves beneath the home. As the soil moves, air pockets, or voids, form. Those voids cannot support the heavy weight of your foundation walls, and thus the walls themselves will start to crack and shift downward—or settle—into those voids. Whether or not this soil shifts evenly underneath your home dictates how much damage your home will incur. Fortunately, foundation settlement is easy to spot before the issue worsens over time, as the tell-tale sign of a settlement issue is vertical or stair-step wall cracks.
The Two Types of Settlement
There are two types of foundation settlement: uniform settlement and differential settlement.
What is normal house settling?
Most buildings will settle at a slow rate. Normal, or uniform, house settling is often unnoticeable but may be accompanied by small drywall cracks that don’t get bigger over time. As the name implies, uniform settlement typically causes the home to settle evenly, leading to very minor damage or no damage at all.
What is differential settlement?
Conversely, differential settlement causes different parts of the structure to settle or heave unevenly. This can lead to interior or exterior foundation wall cracks, building frame distortion, uneven floors, jammed doors or windows, and other structural damage throughout the home.
What Causes Foundation Settlement?
Whether due to uniform or differential settlement, all foundation settling can be traced back to soil movement. There are usually a number of different soil layers underneath a house, and the lower layers typically have a greater soil bearing capacity. Foundation settlement can occur when the structure is built on a layer of soil that can’t support the weight of the home. Uniform settlement typically occurs when the soil beneath your foundation gives into the foundation’s weight. Soil will become more compact over time as the weight of the foundation presses into it. On the other hand, differential settlement can have a number of causes, including expansive soils, soil washout, and poorly compacted fill soil.
1. Expansive Soils
In Georgia, our homes sit atop Georgia red clay, which is an expansive soil in nature. Expansive soils shrink when they are dry and expand when they become oversaturated. Without proper drainage solutions, homes built on expansive soil can become subject to constant soil movement. When wet, the soil can expand and eventually washout. When dry, it will crumble and dry out. Eventually, whether due to washout or dry-out, the soil will erode or shift away, leaving voids.
2. Soil Washout or Dry-Out
Heavy rainfall and flood conditions can saturate the soil around your foundation. Without proper landscape grading and drainage, underground streams can form and wash away the soil underneath your foundation. Your foundation will then sink or settle into the gaps. Droughts or extended periods without precipitation can cause the soil to crumble and erode away, again often resulting in foundation settlement.
3. Poorly Compacted Fill Soil
When your home was built, the builder likely cleared a large plot of dirt to form a properly-graded plot in which to build your house. This is called the Clay Bowl Effect. Afterward, your foundation footing is cast, then your foundation walls erected (if your home sits on a basement or crawl space) and floor poured (if you have a basement). Then the soil that was removed is poured back around the house. The problem is that, unlike the hard, compact virgin soil that was removed, this back-fill soil is loose and granular. This loose soil is automatically more susceptible to washout, dry-out, and erosion than the virgin soil it replaced. When the builders do not properly compact the soil before building the rest of the house on top of the foundation, it can expedite the soil’s expansion, contraction, and erosion around and underneath your home, often yielding settlement at a much faster rate as a result.
Signs of a Sinking Foundation
The signs of a sinking foundation can appear subtle at first—unfortunately, many homeowners can go years before noticing differential foundation settlement. However, as with all foundation causes of foundation damage, foundation settlement is the easiest and least expensive to repair when caught early on.
Here are some common signs that may indicate a sinking foundation:
How to Fix a Sinking Foundation
The first thing you will want to do when symptoms of foundation settlement become visible is contact a foundation repair specialist. At AquaGuard Foundation Solutions, we provide a thorough, comprehensive inspection and estimate for all your foundation settlement repair needs.
We fix foundation settlement issues by installing steel foundation piers. These piers are bracketed to the footing of your house and hydraulically-driven beneath the foundation until they reach load-bearing soils that can permanently stabilize your structure.
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