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What Is Foundation Underpinning?: A Beginner’s Guide

crew installing a push pier to underpin a foundation

Just as your home can settle and sink for various reasons, several options exist to repair and protect it. Underpinning is one such method, available in various forms to suit your home’s unique needs.

Without underpinning solutions, your home will continue to sustain damage, leading to unsafe living conditions for your family.

Learn more about this essential repair method and how local foundation repair professionals can help safeguard your home. 

Underpinning a Foundation: What Is It? 

Underpinning is the process of strengthening an existing foundation by installing additional support below the ground level. The foundation is extended either in breadth and/or depth to distribute the weight of the house over a larger surface area or provide more support. 

The process starts with excavating the soil underneath the foundation. Work takes place in stages to minimize the risk of structural damage. An engineer assesses the soil and determines the appropriate foundation depth. The underpinning solution is installed and repeated until the problematic foundation is strong and stable. 

When Is Underpinning Necessary? 

Underpinning is needed when the original foundation becomes too weak to support the weight of the house. This is usually due to: 

  • Changes in the foundation soil caused by erosion, nearby tree roots, soil expansion and contraction from moisture, foundation settlement, or subsidence
  • Failure to consider soil characteristics during the initial design phase 
  • Changes in the building’s use, especially after a renovation 
  • Natural disasters, such as earthquakes and droughts that move or destabilize the structure 

Are You a Candidate for Underpinning? 

While a professional assessment is always best, the following foundation problem signs should prompt you to take action:

drywall cracks and sticking window
  • Cracks in Floors and Walls: Some cracks are superficial, but larger ones indicate an underlying issue like uneven weight distribution caused by a weak foundation. Look for cracks in the walls, floor tiles, drywall, concrete slab, and brickwork. 
  • Misaligned Doors and Windows: If you have difficulty opening or closing doors or windows or see widening gaps around them, contact a professional. In severe cases, doors may lean, and frames may pull away from the walls.
  • Uneven, Sagging Floor: Floors that lean to one or more sides may indicate a severe foundation problem. 

What Are My Underpinning Options?

Various underpinning solutions are available, and the repair type used depends on your foundation type, its condition, and the extent of damage.

1. Temporary Underpinning Solutions 

Some methods are only temporary solutions, like the ones below. 

a. Mass Concrete Underpinning 

Mass concrete underpinning involves replacing the soil under the foundation and pouring concrete. The soil is contained and placed in a predetermined sequence so as not to compromise the foundation’s bearing capacity. While this may offer some respite to foundational issues, it won’t prevent the foundation from shifting. 

b. Pile and Beam Method 

A mini-pile is installed on either side of the foundation walls, and the brickwork below the wall is removed. The piles are then connected, and the wall is supported using a reinforced concrete needle. This method is suitable when you need to increase the load capacity of the foundation or have restricted access. It is faster than traditional underpinning and offers less disruption, but much consideration goes into its design and implementation, especially concerning corrosion resistance and structural compatibility. 

c. Piled Raft 

This method is convenient if the entire structure needs underpinning. It works when the soil is too hard for small equipment to excavate or the foundation is too deep for ordinary underpinning methods. Piles are placed at predetermined locations, and pockets below the footing are broken. Reinforcing beams are then placed and linked with a ring beam before concrete is poured. On the downside, internal floors must be removed completely before applying the solution. 

2. Permanent Underpinning Solutions 

While temporary repairs can get you by, permanent underpinning solutions make a lasting impact on your foundation. We strongly recommend the following foundation pier solutions

installing helical piers under a house

a. Helical Piers

Similar to giant screws, helical piers are mechanically driven down to the bedrock, anchoring into more stable soil deep beneath the home. They have a variety of applications but help support lighter structures, including chimneys, and can potentially help lift settling foundations. 

crew installing push piers

b. Push Piers

Crafted from galvanized steel, push piers, as the name suggests, are pushed deep into the ground until they reach load-bearing soil. They are also known as resistance piers, as they rely on resistance from the underlying soil to stabilize and possibly raise the foundation back to its original level. 

installing slab piers under a concrete slab foundation

c. Slab Piers

While the previous two systems can be used on various foundation types, slab piers are made specifically for homes with slab foundations. They are also advanced into the ground beneath the concrete slab floor until reaching stable soil for lasting reinforcement. 

Need Foundation Underpinning? Contact Tar Heel Today!

Tar Heel Basement System Crew and work trucks

Foundation settlement and damage won’t go away on their own. It’s crucial to be vigilant of the signs and repair the issue immediately with a customized solution. Underpinning using foundation piers is the best way to ensure your home’s safety and stability.

At the first sign of trouble, request a free foundation inspection and repair quote from the Tar Heel Basement Systems professionals. Our experts will assess your foundation and recommend tailored underpinning solutions for your home. 

Foundation Pier FAQs

Yes, helical piers are versatile and can be used for different foundation types, including concrete slabs, crawl spaces, and basement foundations. Contact Tar Heel Basement Systems for a free inspection to determine if helical piers are suitable for your home.

The timeline can fluctuate based on various factors including the location and extent of the problem, as well as the number of piers to be installed. Get a precise project duration estimate during your complimentary inspection with Tar Heel Basement Systems.

Slab piers are designed specifically to stabilize and potentially lift slab foundations, offering a targeted solution that can address settlement issues effectively. They work by transferring the weight of your home to deeper, stable soil layers or bedrock, bypassing the unsettled and compromised soil that caused the issues in the first place.

Related Resources

Holly Richards-Purpura

Holly Richards-Purpura

Content Writer

Holly is a Content Writer for Groundworks who has written and edited web content for the foundation services industry for almost 10 years. With a background in journalism, her passion for the written word runs deep. Holly lives in Columbus, OH, with her husband. Along with educating homeowners, she also has a big heart for the Big Apple.

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