Foundation underpinning is the process of strengthening and stabilizing the foundation of a building or structure that has experienced settlement or other forms of foundation damage. It is needed when the foundation’s structural integrity has become compromised and weakened due to factors such as soil instability, changes in moisture content, poor drainage, and more.
The primary purpose of underpinning is to prevent further damage to the building or structure and ensure its stability for continued use. It can also help to restore and lift the foundation to its original level, improve its load-bearing capacity, and enhance its resistance to future settlement.
The underpinning process typically involves excavating soil beneath the foundation and adding structural support, such as helical piers, to transfer the building’s weight to load-bearing strata.
- Load-bearing strata refer to the layer of soil or rock beneath the foundation that can support the weight of the building. This is typically the strongest and most stable layer of soil or rock and is the target for foundation underpinning. By extending the foundation to load-bearing strata, the weight of the building can be safely transferred and the foundation can be stabilized.
The most popular form of foundation underpinning is helical pier underpinning. Helical piers are steel shafts with helical blades that are screwed into the ground to provide support and stability for the foundation. They can be installed with minimal disturbance to the surrounding area and can provide immediate load-bearing support to the foundation.
Here’s an overview of how helical pier underpinning is typically done:
- Site assessment: A licensed contractor and/or professional engineer will assess the site and determine the best placement and depth for the helical piers based on the foundation damage, soil conditions, load requirements, and other factors.
- Excavation: The area around the foundation is excavated to expose the foundation footing for helical pier installation.
- Installation of helical piers: The helical piers are screwed into the ground using hydraulic machinery until they reach the recommended depth and torque capacity.
- Bracket installation: Once the helical piers are in place, a steel bracket is attached to the top of each pier.
- Foundation attachment: The brackets are attached to the foundation footing using bolts or other fasteners.
- Load transfer: The weight of the foundation is transferred from the soil to the helical piers, providing stability and support.
- Site restoration: The excavation area is backfilled and compacted, and any landscaping or other site features are restored.
The number of helical piers needed for foundation underpinning depends on several factors, including the weight of the building, the soil conditions, and the depth of the load-bearing strata. A licensed foundation specialist and/or structural engineer can evaluate the building and soil conditions and determine the number and placement of piers needed to effectively stabilize the foundation. This typically involves conducting a site assessment to ensure the proper installation and placement of the piers.
In summary, foundation underpinning is a process of stabilizing or strengthening the foundation of an existing building by extending it to deeper, more stable soil strata or bedrock. Helical pier underpinning is an effective method for addressing foundation settlement and other issues. It offers several benefits, including quick installation, minimal disruption to the site, and immediate load-bearing capacity. However, it is important to work with a qualified professional who has experience with helical pier underpinning to ensure that the process is carried out safely and effectively.