Mass concrete underpinning is a traditional underpinning method where sections beneath an existing footing are excavated and filled with new concrete, extending the foundation’s depth to reach more reliable bearing soil.
It’s one of the oldest underpinning techniques still in use, valued for its straightforward approach and reliability on suitable soil conditions.
What Does Mass Concrete Underpinning Involve?
- Excavating short sections beneath the existing footing
- Pouring new concrete to extend the foundation’s depth
- Working in a sequenced pattern to maintain stability
- Repeating the process around the affected foundation perimeter
Why Is Mass Concrete Underpinning Important?
Because this method relies on straightforward excavation and pouring rather than specialized equipment like pile drivers or hydraulic pier systems, it remains a practical and often cost-effective choice on sites with reasonably stable, excavatable soil. The labor-intensive nature of the work, done largely by hand in confined excavated sections, does mean it typically takes longer than pier or pile-based alternatives.
This method is generally less suitable on sites with very poor soil at any reasonable depth, or where excavation beneath an existing structure poses safety concerns, which is exactly the situation where pile or pier-based underpinning methods tend to be favored instead. Because the work happens in relatively small sections at a time, a full underpinning project using this method can take considerably longer than pier-based alternatives, sometimes stretching over several weeks depending on the extent of settlement. Despite the labor involved, many contractors still consider it the most dependable option on soil that’s genuinely suitable for it. Patience with the timeline is part of what this traditional method requires in exchange for its reliability.
Mass Concrete Underpinning vs. Beam-and-Base Underpinning
Mass concrete underpinning extends the existing footing directly downward with more concrete. Beam-and-base underpinning instead introduces a reinforced concrete beam that transfers load to separate mini-piles or bases, often used when soil conditions make direct extension less reliable.