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Differential Settlement

The result of the underlying soils moving, or sinking unevenly. This settlement causes cracking to the foundation since one side of the structure is sinking faster than the other.

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Understanding Differential Settlement

Differential settlement is the uneven or unequal settling of a building’s foundation. This occurs when the soil under your foundation contracts, expands, or shifts irregularly. Differential settlement causes the structure to settle at a variable rate.   

When this occurs, the affected building develops small or large cracks and gaps in the concrete walls and floors. You may even notice uneven problems with your doors and windows. 

What Causes Differential Settlement?  

Let’s look at some of the reasons that might cause your home’s foundation to sink unevenly.  

Weak Soils  

Highly compressible soils have a weak bearing capacity. Structures erected on such grounds require special footings to help spread the load of the building over a wider area. This will help prevent differential settlement.  

Poorly Compacted Soils  

During the construction of a building, the ground may require artificial leveling and filling to ease the construction process. When adequately compacted, this fill soil provides a substantial base for supporting the foundation. If not properly packed, the ground may settle unevenly under the building’s weight, leading to structural damage.  

Expansive Clay  

Clay soil is one of the worst soil types for building. This is mainly because this soil swells with water during wet seasons and shrinks during the dry months. Soil that behaves this way is highly expansive.  

If your foundation sits on clay soil, you are likely to experience differential settlement after some time. Your footing will settle downwards during the dry seasons as the clay shrinks.  

Bedrock Issues  

The bedrock is one of the strongest supports a foundation can have. This, however, does not mean that it is immune to differential settlement. Sometimes, the bedrock may intercept the footing trenches, causing differential settlement. Hilly and rocky areas tend to have shallow and outcropped bedrocks. Builders find it hard to dig through such soil to cast trench footing. 

Signs of Differential Settlement 

Whether settlement happens in a few months or takes a couple of years, the problems that arise remain pretty much the same. You’re likely to experience multiple issues such as:  

Restoring a Settling Foundation  

Your sinking foundation needs to be underpinned using piers and there are a few ways to do this. What this does is transfer the heavy load to the stable bedrock and stabilize the foundation.   

Helical piers:

Also known as screw piles, helical piers consist of a central shaft with several helix-shaped plates. These piers are versatile and great for supporting light structures such as porches.   

Push piers:

Mechanically driven into the earth, push piers help pass your structure’s weight to the stable bedrock. They’re installed close to the footings and secured in place using brackets. These systems are easy to install and cause little disturbance to the landscape.   

Slab piers:

This type is designed to stabilize or raise sunken slabs. They’re driven into the ground and down to the load-bearing soil. Grout is pumped to fill the gaps under the slab before concrete is poured over the holes. 

Differential Settlement Prevention  

When it comes to foundation issues, prevention is vital. Builders should start by assessing the soil to confirm that it is perfect for the type of structure they want to put up. Ideally, you should build a house on soil layers with minimal clay or silt. This way, you will not have to worry about the soil under your foundation shrinking and expanding. If possible, the house should sit on native soil and not fill soil.  

Before any construction work starts, get a professional to determine the load-bearing capacity of the soil. They will advise you on whether the ground needs some improvements or amendments early enough and whether a deep foundation is necessary. 

At Groundworks, we can help stop your foundation from settling unevenly. If you have any foundation concerns, contact us today to schedule a free foundation inspection and quote and get a lasting fix to your problem. 

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