What is the term for the permanent support that enlarges foundations to provide additional levels?

The term for the permanent support that enlarges foundations to provide additional levels is underpinning. Underpinning involves extending the foundation depth or breadth to improve stability, support additional weight, or accommodate new construction, such as the addition of another level to a structure. This process is essential when existing foundations are deemed inadequate or when modifications to a building necessitate enhanced structural support.

This technique is particularly important in situations where soil conditions may have changed or where a building may have settled over time. The underpinning process ensures that the foundation can handle the increased loads without compromising structural integrity.

The other options do not pertain to the specific process of enlarging and strengthening foundations for added levels. Shoring refers to temporary support structures used during construction or repair. Shell piles are a different type of foundation element used to transfer loads to deeper, stable soils. Flexible bituminous materials are often used in road construction or waterproofing, rather than in foundational work.