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Differential Settlement

Uneven soil settlement beneath a building’s structure may cause different parts of it to sink, causing cracks and other structural issues.

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Foundation problems are a builder’s worst nightmare. How good the structure settles will depend on its weight and the characteristics of the soil under the footing, and sometimes things don’t go as planned. Soil that appears perfect at the onset of construction can suddenly start to sink. Once the building goes up, the weight can become unbearable, and you may start noticing some issues. 

Let’s look at differential settlement, one of the types of foundation settlement that affects many homes across the country.  

Differential settlement

What Is Differential Settlement? 

Differential settlement refers to the uneven or unequal settling of a home or building’s foundation. It occurs when the ground underneath your structure settles because of too much weight. In other words, the foundation is unable to support the load of the building, resulting in some kind of structural damage. 

Settlement happens when the soil beneath the structure expands, contracts, and then shifts. Drought conditions, flooding, tree roots, broken water lines, and poor drainage can cause this problem. 

When differential settlement happens, the building develops small or large gaping cracks in the concrete blocks and the brick veneer. This causes more and more damage to the structure. You’ll also notice uneven settlement in the windows and doors. 

What Causes Differential Settlement? 

Differential settlement doesn’t just occur out of the blue. There are underlying causes that you must watch out for before and during the construction time. Most causes depend on whatever lies below the footing of the structure. Let’s look at some of them. 

Expansive Clay 

Clay is the worst soil type for building because it tends to expand and shrink with weather changes. Clay behaves just like a sponge. It swells with water during wet seasons and shrinks during dry months. The soils that behave this way are highly expansive

If there is massive clay soil beneath the building, you’re likely to experience differential settlement after some time. Your footing will move downward during the dry seasons as clay shrinks. 

Bedrock Issues 

Bedrock is one of the strongest supports a foundation can have. But this doesn’t mean they’re immune to differential settlement. Sometimes the bedrock may intercept the footing trenches, causing differential settlement. Hilly and rocky areas have shallow and outcropped bedrock. Builders find it hard to dig through the soil in such areas to cast trench footing. 

Houses built in such places rest partly in soil and partly in bedrock. This is because the soil will eventually give in to the weight of the structure and settle. The rock will continue to support the building because of its strength and stability. In such a situation, a differential settlement will be unavoidable. 

Other causes of differential settlement include; 

  • Excavation work near a structure 
  • Drying soil surface layers 
  • Trees with large roots close to the building 
  • Different foundation dimensions 
  • Vibration  

Signs of Differential Settlement 

You might start to notice signs or experience differential settlement problems soon after construction. But sometimes, it can take years. No matter how long it takes to occur, differential settlement is dangerous and needs to be addressed quickly. 

Cracks on the foundation walls and concrete slab are some of the first signs something is brewing. Watch out for cracks that appear wider at the top and narrow at the bottom. 

Check your windows and doors. Are they sticking out of their frames? Do they have gaps? When differential settlement occurs, the window and door frames fall out of plumb. They won’t close smoothly as usual. 

It’s also likely that your foundation will move vertically. Floors will also get so out of level that a ball won’t smoothly roll on it. All these are indications that the soil holding your foundation is moving at a rapid rate. 

Bulging walls, tilting chimneys, and sinking exterior stairs are other unmistakable signs of differential settlement. If you’re not sure they’re cosmetic, it’s best to ask your contractor to investigate the issue further. Left unchecked, these can lower the structural integrity of a building. 

Resolving Differential Settlement 

If you notice any of the above problems with your house, you need to consult a foundation repair expert as soon as possible. 

The settled foundation has to be underpinned and the ground treated properly. Underpinning helps transmit the load that’s causing the foundation to sink to the load-bearing strata. Piers can also be driven down the foundation and left to rest at the hard rock level. 

When it comes to foundation issues, prevention is always better than a cure. Builders can protect every building from differential settlement by ensuring the soil is perfect for their type of construction. Buildings need to be constructed on soil layers with little clay or silt. This way, the soil under the foundation will not shrink or expand. Also, ensure your building sits on native soil and not fill soil. 

Before any construction work starts, get a structural engineer to determine the load-bearing capacity of the soil. They will determine if the soil needs some improvements or amendments early enough and whether a deep foundation is necessary. Sometimes, the solution may be as simple as extending the foundation to improve the soil’s load-bearing capacity. 

If you are experiencing foundation settlement, contact the experts at JES Foundation Repair to schedule a free foundation inspection and repair quote. Our crew will inspect your foundation and apply the appropriate fix to raise the foundation and stabilize it.

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