Underpinning vs Foundation Support: What’s The Difference?

Underpinning and foundation support are related construction techniques, but they serve slightly different purposes and involve distinct methods. Here’s how they differ:

1. Purpose:

• Underpinning: Underpinning is a specific technique used to strengthen and stabilize an existing foundation that has settled, shifted, or become unstable. It’s employed when the original foundation is failing, and the goal is to provide additional support and prevent further settlement.
• Foundation Support: It is a broader term that encompasses various methods and materials used to ensure a stable and secure foundation for a new or existing building. Therefore, it includes techniques like using helical piers, concrete piers, piles, and grade beams to support the weight of a structure.

2. Timing:

• Underpinning: Underpinning is typically done as a remedial measure after a foundation has shown signs of distress or settlement. It’s a corrective action taken to address an existing problem.
• Foundation Support: It can be implemented at the outset of a construction project to ensure that the foundation of a new building is stable from the beginning. It’s also used in retrofitting or reinforcing an existing foundation to prevent future problems.

3. Method:

• Underpinning: Underpinning often involves excavating sections of the existing foundation and then strengthening or extending it to a deeper and more stable soil layer. Common methods include injecting concrete or installing piers beneath the existing foundation.
• Foundation Support: Foundation support methods can vary widely and may include the use of helical piers, concrete piers, piles, grade beams, or other engineered solutions. The choice depends on factors like soil conditions, building load, and project requirements.

4. Problem Addressed:

• Underpinning: Underpinning specifically addresses issues related to an unstable or settling foundation. It’s a reactive measure taken to correct foundation problems.
• Foundation Support: Foundation support is a proactive measure taken to prevent potential foundation issues in new construction or to provide additional stability to an existing foundation even if no obvious problems are present.

In summary, underpinning is a technique used to fix or strengthen an existing foundation, especially when it’s experiencing problems, while foundation support is a broader term encompassing various methods used to ensure the stability and longevity of a foundation, whether in new construction or retrofitting existing structures.

The choice between these approaches depends on the specific circumstances and goals of the construction project.