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    A Brief Guide to Pile Raft Foundation


    Piled Raft Foundation has two construction techniques, combined in one. This foundation building method is not used in all types of buildings. It is designed for certain situations only and is referred to as a hybrid design style.

    What is the Pile Raft Foundation?

    For better understanding, we can break down the two concepts. A raft, also known as a spread, lays out a load of an entire building, across the ground. On the other hand, piles are columns that are installed beneath the surface and are connected with the top of buildings.

    In a pile raft foundation, both the raft and the pile are combined together to build the foundation of a building.

    When is it important to use a Raft?

    A Piled Raft Foundation is not used for all types of foundation building purposes. This is usually utilized when no solid foundation or good soil condition is accessible near the ground surface. To simply put it; the soil condition is poor and quite unstable to build a solid foundation on. Thus, a raft is used to spread an even foundation, across the ground surface, offering stability.

    When is it important to use a Pile?

    Piles are installed into the ground, where the platform is a bit stable. There are different piling materials being used these days. It is usually bedrock but can be any other as well. Your engineer is going to determine the size and number of the pile, depending on the size and weight of the building.

    When are the two combined?

    So when is the pile raft foundation utilized, combining both the foundation building techniques together? Now, this building method is used in rare situations. It is mandatory when the materials that are anchoring the piles are questionable in their stability. Also, this foundation method is used when the material is not extending entirely under the building.

    Thus, pile raft foundation is best for circumstances where piles and rafts both are in a questionable state. The engineer is the sole person to decide whether this method is required or not.

    Design of Pile Raft Foundation:

    The designing procedure of a pile raft foundation is extremely complicated, depending on the condition of the soil that the building has to stand on. It is usually carried out by engineers and architects after thorough soil testing.

    Pile placement is not always extremely uniform. Thus, many times, the design process calls for several specific placements and can be time consuming too. From the strength of the piles to the positioning, a lot goes into consideration for the designing of a perfect pile raft foundation.

    Factors that Affect Pile Raft Foundation

    There are different things that can affect the pile raft foundation. Several studies and observations have been performed to take a deeper look into the elements that can have an impact on this technique. According to experts, the following factors might impact the foundation:

    • Length of piles
    • Number of piles
    • The spacing ratio of piles
    • Stiffness of piles
    • Thickness of raft
    • Dimensions of raft
    • Stiffness of soil
    • Type of soil

    This is the major reason why an extremely professional team must undertake the process of Restricted Access Piling. Several factors can have an impact on it and thus, it must be designed and constructed carefully.


    Hiring an expert team for pile raft foundations is very crucial. With an insight into this foundation building technique, you would now understand the complexity of the procedure and the importance of it as well. Thus, always take your time before choosing contractors for any construction project.

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