Key Facts

• Underpinning is essential for reinforcing foundations when dealing with issues like settling or cracking.
• Various methods exist, including pit underpinning, expansion piles, piers, and jacketing.
• Cost and effectiveness vary by method, depending on the specific soil conditions and structural needs.

Underpinning Methods

Pit Underpinning

Pit underpinning involves excavating around the foundation and pouring large volumes of concrete beneath it. This technique is beneficial for addressing structural issues related to loose or inadequate soil supporting a building.

Expansion Piles

Expansion piles are steel structures that expand under load, effectively transferring loads to more secure soil layers. They create friction with the surrounding soil, aiding in stabilization. Expanded concrete piles differ by shifting load along their entire length, minimizing lateral forces on foundation walls and reducing soil pore pressure.

Stumps

Stumps, often seen in landscaping, can pose hazards and consume valuable space. While typically referring to tree remnants, the term has political connotations as well. In the context of foundation work, stumps may require professional removal if they compromise structural integrity or safety.

Piers

Pier foundations transfer building loads to steel or concrete pillars reaching solid bedrock. They stabilize structures in areas with soft clay soils above firmer layers. Concrete piers and drilled caissons are commonly used, providing significant support while allowing minimal disruption to the surrounding environment.

Jacketing

Jacketing enhances the strength of structural columns, particularly when increased loads or damage occur. Reinforced concrete jackets improve a column’s ductility, shear capacity, and overall stability, accommodating changes in structural demands.

FAQ

What is underpinning?

Underpinning is the process of strengthening existing foundations by transferring loads to deeper, more stable soil layers.

What are the different methods of underpinning?

Common methods include pit underpinning, expansion piles, piers, and jacketing, each offering specific benefits based on soil conditions and structural requirements.

Why are expansion piles beneficial?

Expansion piles create friction with the soil when loaded, stabilizing the foundation and minimizing lateral forces, which can reduce soil pressure and improve overall foundation support.

How do piers help with foundation stability?

Piers extend the load from a structure down to solid bedrock, providing support in areas where weaker soil layers are present, thus preventing future structural movement.

What is jacketing used for in construction?

Jacketing is employed to reinforce structural columns, enhancing their load-carrying capacity and stability, especially after damage or increased load.

How can I tell if my foundation needs underpinning?

Signs that your foundation may need underpinning include visible cracks, uneven floors, or doors and windows that stick, indicating potential settling or shifting.