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Underpinning

Underpinning helps reinforce the base of buildings and homes built on poorly compacted or otherwise compromised soils.

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Your home’s foundation will change over time. Whether it’s a couple of months after construction or several years later, these changes will reduce the amount of load that a foundation can support. Weak or shifting soils take the lion’s share of the blame.  

As a result, the foundation may crack or settle unevenly, and this could jeopardize your safety and your home’s structural integrity. Lucky for you, there’s a way out, and that’s underpinning the foundation. Read on to learn more about underpinning and your options for repairing your sunken foundation. 

underpinning foundation

What Is Underpinning? 

Underpinning refers to the process of supporting and strengthening the base of a home or a building by extending its foundation deep. What this does is distribute the load above over a wider area. 

Every underpinning job starts with digging out areas of soil underneath the foundation. Excavation is done in stages to lower the risk of damage, which can lead to structural issues. A structural engineer determines how deep the foundation goes. They do this by assessing the soil and identifying the right strata for the structure. 

After the underpinning material is applied, the process is repeated elsewhere within the foundation until the whole structure becomes strong. 

When Should You Use Underpinning? 

There are many reasons why homeowners across Missouri underpin their homes or buildings. Some people reinforce the foundation if it’s not strong enough to support their home. Others underpin their foundation when they realize the soil conditions weren’t factored in during construction. 

Sometimes, the purpose of a structure or a building changes after renovation. This will compel the owner to underpin it. Also, whenever there’s new construction near an existing foundation, the old foundation has to be underpinned. 

If you’re planning to add a story or two above the top floor, you will have to underpin the building to enhance its foundational strength. You may also find it necessary to underpin your structure after a severe drought or whenever a tremor shakes its base. 

Underpinning Solutions and Techniques 

When it comes to reinforcing your foundation, you have the following options on the table: 

Pile method: In this method, contractors install piers evenly along the base to lift it and to transfer the structural load to the stable bedrock below the ground. It’s suitable for fixing foundations that rest on either soggy soils or expansive soils like clay. This is the most common and long-lasting method. 

Pit method: Here, the contractor divides the foundation into sections, drills holes on the retaining walls, and attaches a supporting needle with a bearing onto the foundation. 

Mass pouring: When the foundation requires shallow underpinning and not deep excavation, mass pouring will suffice. The weak underlying soil is first dug out then concrete is poured to bolster the base of your structure. 

Temporary Underpinning  

Some foundations experience minor settling or issues. If this happens to yours, a contractor might recommend one of these fixes: 

Concrete Piers: These are short and precast concrete cylinders that are driven into the soil. They go on top of each other and are head with a wire. Shims are then placed right on top of the uppermost cylinder then the soil backfilled. The downside to this method is there’s nothing to guide the pillars. As a result, they don’t go deep into the soil. 

Concrete Underpinning: Soil is first dug out around your foundation then concrete footings poured below the existing footings. Soil is backfilled when the concrete cures. While this solution can help extend your footing, it won’t prevent foundation movement. 

Permanent Underpinning Solutions 

If you want to address serious settlement issues, you should consider these long-lasting underpinning methods

Push piers: Going several feet deep, push piers help permanently stabilize and can help raise a sinking foundation to its original elevation. They’re made from galvanized steel and usually driven to the stable bedrock. 

Helical piers: These piers look like giant screws and are driven mechanically to the ground until they reach the bedrock. We usually use them to reinforce the base of lighter structures. 

Slab piers: Contactors use slab piers to support and strengthen concrete slab foundations. The piers are driven deep into the stable soil, stabilizing your home and potentially lifting the slab and interior walls back up. 

If your home’s foundation is slowly caving in due to shifting soils or other reasons, contact Foundation Recovery Systems to schedule a free foundation inspection. We’ll take a closer look at your foundation then recommend a solution to stabilize it for good, giving you peace of mind and a safer home.