What is the purpose of underpinning in construction?

• A. To enhance the aesthetic appeal of a structure
• B. To strengthen the foundation of an unstable or weak structure
• C. To increase the height of an existing structure
• D. To waterproof the foundation of a building

Answer: (B)

Underpinning serves a critical role in providing support and stability to a structure with an unstable or inadequate foundation. The process involves extending or strengthening the existing foundation to prevent further settlement or structural failure, which can occur due to various factors such as soil erosion, water-related issues, or changes in the load imposed by the structure.

The primary goal of underpinning is to improve the load-bearing capacity of the foundation by transferring the structure's weight to deeper, more stable soil or bedrock. This is especially important for older buildings that may have experienced subsidence or those constructed on unsuitable soil types. By effectively addressing these foundation weaknesses, underpinning helps ensure the longevity and safety of the structure.

Other options do not accurately represent the purpose of underpinning. Enhancing aesthetic appeal refers to decorative aspects of construction, not structural support. Increasing the height of a structure involves different methods that don't necessarily relate to foundation stability. Lastly, waterproofing of a foundation is concerned with moisture protection rather than addressing foundational weaknesses that underpinning specifically targets.