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What Is Foundation Underpinning?

underpinning methods

Changes in soil composition do affect the foundation of many buildings and structures. The culprit is often shrinking or weak soil. Because they’re shifty, the foundation has to be reinforced. Otherwise, it will settle, crack, or crumble. This isn’t good for a building’s structural integrity.

Let’s look at what is underpinning and the different types of underpinning products in the foundation repair industry.

What Is Underpinning?

Underpinning is the process of bolstering and supporting the foundation of a building, house, or structure. It entails reinforcing the existing foundation and strengthening the underlying soil by extending the foundation so that the load above is evenly distributed over a larger surface.

The underpinning process begins by excavating and removing the soil directly under the foundation. Soils are removed in stages to minimize the risk of undermining the foundation, which can lead to structural problems. The depth of excavation is determined by a structural engineer, who examines the soil and identifies the strata that’s suitable to hold the load.

Once the soil is replaced with the underpinning material, the process is repeated in the next section of the foundation until the entire structural base is reinforced.

When Your Home Needs Foundation Underpinning

Homeowners turn to underpinning for a variety of reasons, often when the existing foundation isn’t robust enough to support the structure or when the property has undergone significant changes. For instance, underpinning is the go-to method when:

  • The original construction was subpar, with issues like improper soil compaction or leveling.
  • The property’s usage changes, such as converting a residence into a business or adding more stories to your home.
  • Soil properties weren’t considered during the initial building design and construction.
  • Nearby construction necessitates excavation of the soil supporting the current foundation.
  • The property owner wants to bolster the foundation’s capacity, like when adding another floor.
  • The structure becomes unstable due to earthquakes or droughts.

Signs of Foundation Damage That May Require Underpinning to Repair

Identifying the need for underpinning requires careful observation and assessment. Here are the telltale signs that your house might need underpinning:

  • Visible Foundation Cracks: Keep an eye on the size, number, and direction of the cracks in your foundation walls or floors. Horizontal or stair-step cracks are particularly concerning.
  • Uneven or Sloping Floors: Floors that are no longer level or have started to slope could indicate foundation settlement.
  • Doors and Windows Misalignment: Difficulty opening or closing doors and windows, or noticeable gaps and misalignment between frames, could hint at foundation movement.
  • Sagging or Bouncing Floors: Spongy, sagging, or bouncy floors may be due to compromised foundation support.
  • Gaps and Spaces: Look out for gaps between the floor and the wall, especially near room corners.
  • Cracked or Leaning Chimney: This is often a visible sign of foundation problems.
  • Plumbing and Drainage Issues: Recurring leaks, water pooling around the foundation, or slow drainage can signal foundation issues.

If you notice any of these signs or have concerns about your foundation, it’s best to consult with a professional. They can conduct a thorough inspection and provide advice on whether underpinning is necessary. We offer free foundation inspections at JES to help you understand the condition of your home and determine the best course of action.

Types of Underpinning

When reinforcing the foundation, contractors use the following methods. Let’s look at what each entails.

1. Foundation Piering

In this method, foundation piers or piles are installed evenly along the foundation to lift it and transfer the weight of the unsteady concrete to the stable bedrock. It’s immensely useful in fixing foundations built on expansive or soggy soils.

There are three basic kinds of foundation piers:

  • Push Piers: The most commonly used type of piers for stabilizing and potentially lifting a settling foundation back to level. These galvanized steel push piers are driven to bedrock and load-bearing strata to better support the weight of the home.
  • Helical Piers: Helical piers serve the same purpose as push piers and are screwed down mechanically into the earth till they reach stable soil. These systems are best used to support the foundation of lighter structures like chimneys and patios.
  • Slab Piers: Contractors use slab piers to support and strengthen concrete slab foundations. The piers are driven deep into the stable soil, securing your home and lifting the slab and interior walls back up.

2. Pitting Methods

The foundation is divided into sections, holes are drilled on the foundation wall, and a supporting needle with a bearing is attached to hold the foundation. A pit is excavated and a new foundation is created beneath it.

3. Mass pouring

It’s used in situations that require shallow underpinning, not deep excavations. The weak underlying soil is dug out and concrete poured in its place to strengthen the foundation.

4. Temporary Underpinning

If your foundation problem isn’t severe, foundation experts can underpin the structure of the home with either of these solutions:

  • Concrete Underpinning: Soil around the foundation is dug out and huge concrete footings are poured under the existing footings. Once the concrete dries up, the soil is backfilled. What this does is extend the footing. However, it won’t stop the foundation from shifting.
  • Concrete Piers: These are short and precast concrete cylinders that are driven into the soil. They go on top of each other and are secured with a wire. Shims are then placed right on top of the uppermost cylinder and the soil is 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.

Are There Downsides to Underpinning?

While underpinning can be an effective solution for foundation issues, it’s important to consider the potential disadvantages associated with the process. Here are some drawbacks to be aware of:

  • Cost: Underpinning can be a significant investment. The cost depends on various factors, including the size of the project, the chosen underpinning method, and the extent of the foundation issues. It’s essential to budget accordingly and consider the long-term benefits when evaluating the cost.
  • Moderate Disruption: Underpinning involves excavation and construction work around your home’s foundation. This process can cause disruptions to your daily life, such as noise, dust, and restricted access to certain areas of your property.
  • Time-Consuming: Underpinning is not a quick fix. It requires careful planning, engineering assessments, obtaining necessary permits, and executing the construction process. Homeowners should have realistic expectations regarding the timeframe involved.
  • Landscaping Impact: Excavation work associated with underpinning can potentially impact your landscaping and outdoor spaces. Trees, shrubs, and other vegetation near the foundation may need to be removed.

Despite these disadvantages, underpinning remains a valuable solution for addressing foundation issues and ensuring your home’s long-term stability.

Contact an Expert for More on Underpinning Foundations

If your foundation is crumbling due to weak soils or any other issue, contact JES Foundation repair and request a free assessment. We’ll determine the problem and install the appropriate underpinning solution.

Curious about foundation underpinning? It’s a term you may have heard tossed around by homeowner friends and experts alike, but it’s not always clear what it means. Essentially, underpinning strengthens your foundation and ensures your home’s long-term stability by reinforcing the existing building foundation.

Foundation Underpinning FAQs

Yes, push piers are designed to stabilize and lift settled foundations. They are installed beneath the foundation and driven deep into the ground until they reach stable soil. Once in place, the piers can be used to lift the foundation back to its original level by exerting hydraulic pressure. 

Foundation pier installation is a specialized task requiring expert knowledge, skills, and equipment. It is not advisable to undertake this task independently. Rely on JES Foundation Repair’s expertise for assured quality installation of foundation piers.

Helical piers offer a more cost-effective solution compared to many other foundation repair methods, providing a robust and economical choice for homeowners. 

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