Reddy Kancharla – An Overview on Constructing Raft Foundations for Buildings

Raft foundations are concrete slabs of uniform thickness with reinforced steel beams that support the structures and columns. These slabs generally cover the entire contact area beneath the building or a significant part. The slabs spread out the weight of the building over a large area to ensure even stress distribution on the ground soil. The construction of raft foundations is ideal in areas where the ground soil has a low bearing capacity. This is impossible with other shallow foundations such as a traditional trench or pile footing. However, the earth still needs to support heavy structural loads.

Reddy Kancharla is a leading civil engineer from New York City with over 25 years of valuable experience under their belt. His areas of expertise are civil construction, construction quality control, and geotechnical consultancy. However, he has extensive industry-based knowledge in many other fields of civil construction. These include assessing structural failures, remedial designs, rectifying structural discrepancies, executing ISO quality control standards, and scheduling construction projects.

 Throughout his illustrious career, he has held crucial managerial level positions in many prominent construction firms in the city. He is even the brainchild behind success construction of famous high-rise buildings like Goldman Sachs, Bloomberg, and 7 WTC, The USTA National Tennis Center, Yankee Stadium and Giant/Jets Stadium, Terminal No. 1,4,5 and 7 of JFK Airport, and Park Avenue viaduct rehabilitation and the Second Avenue subway, New York.

In this opinion, civil engineers first need to instruct construction workers to excavate the ground to a uniformly flat level. The depth of the excavation should be around10 feet below the ground level. This is the place where the natural soil is solid and compact. Then, the workers place a water-resistant plastic sheet on top of the soil before pouring a 3″ layer of cement concrete. This creates a perfectly flat level base for the raft foundation. Once the concrete hardens, the workplace another water-proof plastic sheet before installing reinforcement steel beams for the raft foundation. Finally, the workers pour a layer of cement concrete over the steel structure up to a specific thickness. This ensures the building’s foundation can withstand heavy structural loads.

Before commencing the construction of the raft foundation for a building, civil engineers need to first:

• Conduct a site investigation to assess the soil conditions and sub-soil rock formations accurately,
• Identify, evaluate and resolve any potential land contamination issues,
• Select the proper insulation to place over the raft foundation to avert cold bridging,
• Make sure there mechanically compact hardcore sub-base for leveling the ground soil, and
• Ensure the steel reinforcement beams making up the raft have the necessary internal stiffnesses.

According to Reddy Kancharla, raft foundations are ideal for large commercial buildings and residential houses. These properties’ footprints and structural loads tend to be reasonably small. Moreover, the soil on which the properties are being built has a low bearing capacity. This necessitates the need to construct the foundation over a large area.