Where are raft foundations used?

Areas with Weak or Unstable Soil

In locations where the soil is not capable of supporting concentrated loads, raft foundations are used to spread the weight over a larger area, reducing the stress on the soil. This approach is particularly effective in preventing foundation settlement and ensuring the long-term stability of the structure, making it an essential technique for constructing buildings in challenging ground conditions.

Buildings with Heavy Loads

Large, heavy structures such as industrial buildings, warehouses, and large commercial complexes often use raft foundations to evenly distribute their massive loads. This distribution helps in minimising the risk of structural failure due to uneven loading or settling, thereby enhancing the safety and durability of these substantial constructions.

Low-Rise Residential Buildings

In residential construction, particularly for single-story or low-rise buildings, raft foundations can be a cost-effective and efficient solution, especially in areas with expansive clay soil or other problematic soil types. By providing a solid base that spreads out the load, raft foundations help prevent damage from soil movement, ensuring the longevity and integrity of the home.

Areas with a High Water Table

Raft foundations can be designed to resist buoyancy in areas with a high water table, making them suitable for waterfront properties or areas prone to flooding. This adaptability not only protects the foundation from water damage but also secures the building's structure against shifting and settling caused by fluctuating moisture levels in the soil.

Sites with Limited Access

In urban areas or sites where space is restricted and access is limited, raft foundations can be advantageous because they require less excavation and ground preparation compared to other foundation types. This characteristic makes them ideal for redevelopment projects or constructions in densely populated areas, where minimising disruption and construction time is crucial.

Construction on Reclaimed Land

For buildings constructed on reclaimed land, which may not be as stable or strong as natural soil, raft foundations can provide the necessary support by distributing the load across a wider area. This technique is essential in ensuring that buildings on such lands remain safe and stable over time, despite the potentially compressible nature of the fill material.

Buildings Requiring Uniform Settlement

To prevent differential settlement in buildings that need to remain level, such as those housing sensitive equipment or with strict operational requirements, raft foundations can offer a solution by ensuring that any settlement occurs uniformly. This uniformity is critical in maintaining the functionality and accuracy of delicate instruments and machinery, which could be adversely affected by even minor shifts in the building's foundation.

Expansive Soils

In areas with expansive soils that swell when wet and shrink when dry, raft foundations can mitigate structural damage by accommodating soil movement and distributing the building load to reduce stress on the foundation. This approach helps in preventing cracks and other forms of structural distress that can arise from the cyclic expansion and contraction of the soil, thus preserving the building's structural integrity over time.