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Understanding the Underpinning - The Support System for Buildings

Understanding the Underpinning - The Support System for Buildings

November 29, 2023

Underpinning is a crucial element of construction that ensures the safety and longevity of a structure by reinforcing its foundation. As its name suggests, underpinning is a process that involves laying a firm underlying support or strengthening an existing foundation of a building. If a structure’s existing foundation is found to be inadequate, whether due to changes in the soil that supports the structure, or if additional stories are to be added, underpinning comes into play to solidify and stabilize the building's base.

Human structures are like the human body; the foundation is equivalent to our feet, bearing the weight of the entire building. Just like our feet need a firm footing to support us, buildings must have a robust and sturdy foundation to bear its weight and remain upright. Unequal or unexpected soil movement can lead to instability, manifesting as cracks and shifts in the building. Here is where underpinning becomes vital.

Underpinning involves excavating sections beneath the existing foundation and filling the dug portions with new foundation material, usually made of concrete, followed by robust reinforcement. In other words, underpinning is akin to providing a failing structure with new 'feet', making it stronger and more resilient to bear the weight of the building.

However, underpinning is neither a hasty nor a straightforward task. It begs meticulous planning and should be performed by skilled professionals who understand the delicate nature of the process. Engineers are tasked with conducting a thorough examination of the structure and its issues before determining the appropriate underpinning technique. Several factors are taken into account, including the type of soil, depth of the foundation, and the building's weight and height.

There are several techniques used in underpinning. The simplest is mass concrete underpinning, also known as traditional underpinning, where concrete is directly poured into excavations made beneath the existing foundation. Another common method is beam and base underpinning, where a reinforced concrete beam redistributes the building’s weight to concrete bases formed at strategic locations. A more modern approach is mini-piled underpinning, which comes in handy when ground conditions are poor. This technique involves drilling piles into the ground at a depth between 2 to 15 metres, providing reinforcement to weaker soil.

Underpinning is not a one-size-fits-all solution. The chosen method will depend on a variety of factors, ranging from the type and structure of your building to soil characteristics and the depth of excavation required. Therefore, it must be undertaken by professionals who will thoroughly analyze the situation before deciding on the most appropriate underpinning method to use.

While underpinning serves to repair and fortify a failing foundation, it is also increasingly utilized as a preventative measure. To avoid potential structural problems in the case of additional levels or expansions planned for a building, underpinning is carried out proactively to strengthen the existing foundation and accommodate the increased loads.

In conclusion, underpinning, while a complex process, is an indispensable aspect of building construction and maintenance. By reinforcing a building's foundation, underpinning ensures the structure's safety, prevents potential damage, and enables enhancements, while extending its life by offering improved stability and durability. A robust underpinning job guarantees that a building stands tall and sturdy, providing a safe and secure space for occupants.